Dean Winchester and Castiel initially had a working relationship, as well as mutual respect for each other. Over time, Dean begins to see Castiel as part of the family. Castiel respects Dean and helps him whenever he can. It is Dean who calls Castiel by the pet name "Cas" which is adopted by many other characters.
When Castiel's betrayal is found out, Dean and Castiel's relationship is severely strained, but overtime, especially when Dean did everything he could, fighting against all kinds of monsters, to save Castiel and get him out of Purgatory, they eventually reconciled.
Having spent forty horrific years in Hell after being dragged there by relentless hellhounds, Dean is miraculously rescued by the angel Castiel who later tells Dean "I'm the one who gripped you tight and raised you from perdition." This rescue mission marked Dean's left shoulder with the handprint of the angel. Initially, Dean suspected Sam as his deliverer, but when this proves to be wrong (Sam adamantly denies this during a verbal confrontation), the brothers, with Bobby Singer's assistance, seek the help of a psychic, Pamela Barnes. From her, the brothers learn of the angel's name, although her disobedience against Castiel's injunction to abstain from beholding his visage resulted in her eyes being burnt out of her skull. Prior to this unfortunate event (for Pamela, that is), Castiel had tried to communicate with Dean, but his true voice is beyond a human being's capacity to hear and thus, failed to establish any meaningful contact.
Castiel first physically appears when Dean summons Castiel to a barn where he and Bobby Singer have all kinds of traps around the room; however, the traps and guns that Dean and Bobby use have no effect on Castiel. Dean asks Castiel what he is, Castiel answers that he is an angel of the Lord.
Dean initially refuses to believe this, though he eventually comes around. Castiel is next seen when he comes to Dean after the rising of the witnesses. Dean asks why the angels didn't come to help, and Castiel responds by saying angels have better things to do than "perch on your shoulder".
When Dean continues to be rude, Castiel loses his temper, and tells Dean that, he should show him some respect because as Castiel was the one who took Dean out of Hell, Castiel can just easily change his mind and throw him back in.
Castiel comes to Dean later on and says, "You have to stop it." He sends Dean to the past (In The Beginning), leading Dean to assume that he has to kill the Yellow-Eyed Demon. When he fails, and in fact indirectly assists in the future being set, Castiel takes him back to the future, and uses the experience as an example of destiny.In It's the Great Pumpkin, Sam Winchester, Castiel comes to Dean again with Uriel, telling Dean they plan to destroy the town to protect the seal, and that he and Sam should vacate. Dean is outraged that they are even considering the plan, and tells them he's not going anywhere, and that he'll stop the seal from breaking himself. Castiel later reveals to Dean that their true orders were to follow Dean's commands, much to Dean's surprise. In the same conversation, Castiel admits to Dean that he has doubts about the orders of Heaven, and tells the older Winchester that he doesn't envy Dean's fate.
The next time Dean sees Castiel is near the end of I Know What You Did Last Summer, when the angels come for Anna Milton. Despite Castiel being part of the team coming to take and kill Anna, Dean saves Cas from Alastair in Heaven and Hell. Castiel repays him by stopping Uriel.
In On The Head Of A Pin, Castiel recruits Dean to help them find out who is killing angels. They want Dean to torture Alastair for information. When Dean begs Castiel not to make him open that door, Castiel admits that he's been demoted, primarily due to his affection for Dean. Castiel tells Dean he wishes he didn't have to ask him to do this, but it is necessary. Castiel manages to talk Dean into doing the torture, but clearly regrets it. When Alastair overpowers Dean, Castiel comes to Dean's rescue. Castiel is also overpowered, but is saved by Sam.Castiel stops by Dean's hospital room and talks to Sam a bit before investigating why the devil's trap broke. Castiel then talks to Dean. By the end of the conversation, Castiel has admitted that it was Dean who began the breaking of the seals, the fall of a righteous man in Hell being the first of the seals.
In The Monster at the End of This Book, Dean asks for Castiel's help for the threat of Lilith coming for Sam. When Castiel tells Dean he can't, Dean tells Castiel to never ask for help from him again. However, Castiel slyly goes into great detail about exactly why he can't help, giving Dean the knowledge necessary to stop Lilith.Although Castiel finds out something and attempts to get this information to Dean, unfortunately Castiel is dragged back to heaven in The Rapture. When he returns, he tells Dean that he does not take orders from Dean. Dean is not sure how to deal with Castiel's new attitude. But he still asks for help when Sam is detoxing from demon blood. Castiel makes Dean swear himself to the service of heaven and makes him wait till they call him in When the Levee Breaks.
In Lucifer Rising, Zachariah calls on Dean, and he later finds out that the angels don't intend to stop the breaking of the seals. Castiel is clearly conflicted about the revelation, and is unable to look Dean in the eye. Castiel refuses to allow Dean to see Sam, and traps Dean in the Beautiful Room. Castiel returns later when Dean tries to call Sam, notifying him that he's "outside his service range."
When Dean asks Castiel why he came, Castiel attempts to mend fences. Dean responds by punching the angel (though this hurts Dean's hand more than Castiel's face). When Dean demands to know why they would do this, Castiel tells Dean, "I see nothing but pain here! I see inside you — I see your guilt, your anger, confusion… in paradise, all is forgiven. You’ll be at peace. Even with Sam." Dean is shocked by this and tells Castiel to shove it. Dean asks Castiel what happened, and reminds him that he was going to help him before. Castiel asks what Dean would have him do. Dean tries to talk him into helping, but Castiel refuses, though it's plain he's anything but content with his decision.
Castiel ultimately decides to help the Winchesters, and comes back. He helps Dean escape by banishing away Zachariah, then tells Dean that Lilith is the final seal, and that they have to stop Sam from killing her. He transports them to Chuck Shurley's home to find the location of Sam and Lilith, but is attacked by Raphael, the archangel in charge of protecting Chuck. He transports Dean to stop Sam and makes his final stand against Raphael.
- "You know, it's kind of funny, talking to a messenger of God on a cell phone. It's, you know, like watching a Hell's Angel ride a moped."
"This isn't funny. Dean. The voice says I'm almost out of minutes."
- —Dean and Castiel[src]
Castiel is resurrected by God (it is believed) and comes to Dean's rescue when Zachariah attempts to force Dean to say yes to Michael. Cas makes Zachariah return Sam and Dean to normal, and scares the angel off. When Dean questions how Castiel could be there, Cas admits that he's just as confused as they are, and then uses his power to carve Enochian sigils into Sam and Dean's ribcages, hiding them from all angelic beings.
Castiel briefly returns, in Good God, Y'all, to ask Dean for his amulet, as it apparently has the power to find God. Dean initially refuses and mocks Castiel's plan to find God. Castiel quickly loses his temper, and tells Dean under no uncertain terms that after all he, Castiel, has done for the Winchesters, he can keep his opinions to himself and give him the amulet.
In one episode, Castiel is angry with Dean and looks at him resentfully, Dean says "The last time someone looked at me like that, I got laid." Castiel continues the expression until a door closes.
In Free To Be You and Me, Castiel and Dean team up to look for Raphael, the archangel who killed Castiel. When asking for Dean's help, Castiel tells Dean that Dean is the only one who will help Castiel, implying that Dean is the only friend Castiel can trust. They first hit the police station and question the policeman who wtinessed the archangel. Castiel mentions angels and demons but Dean quickly covers for them. They find Raphael's empty vessel and Castiel gets ready to face him, though he admits that the confrontation is likely to end with Castiel dead.
While waiting for the showdown, Dean takes Castiel to a brothel so Cas won't "die a virgin". Dean, entirely in his element, is amused at Castiel's clear terror and discomfort at their surroundings. Dean attempts to set Castiel up with a young prostitute, but it ends badly when Castiel assures the woman that it wasn't her fault her father left, terrifying and enraging her. Dean and Castiel both hurry out, though Dean is in stitches over the situation.
Castiel and Raphael confront each other later, with Raphael telling Castiel that God is dead. Castiel refuses to believe this, and leaves Raphael trapped in a ring of holy fire. While Dean attempts to cheer Castiel up, he ultimately runs him off by blustering that he enjoys being alone, having parted ways with Sam earlier.
Castiel continues searching for God and helping Dean. When Castiel finds out Anna is back, and that she is after Sam and Dean's parents, he plans on going into the past to stop her. Though initially reluctant to take the Winchester brothers with him, he ultimately agrees. He is severely weakened by the trip, passing out and gagging on blood when they arrive in the 70s, and then falling into a brief coma when he returns to the present.When a case Dean and Sam are working on leads them to hearts with Enochian sigils carved on them, Dean calls Castiel in for assistance. While they initially believe that a rogue cupid is killing people, the true culprit, Famine, affects Castiel through his vessel, Jimmy Novak, who apparently has a craving for hamburgers. Castiel stuffs himself throughout the episode, much to Dean's disgust, and asks Dean why he hasn't been put under Famine's curse. When Dean explains that he doesn't deny himself anything, Castiel asks, "So you're just well-adjusted?" The original plan to kill Famine was to send Castiel in; however, this ends badly when Castiel is distracted by a slab of raw ground beef. Later, after Famine is incapacitated and Sam is locked up to go through detox, Castiel attempts to comfort Dean, though it doesn't appear to work.
When Sam and Dean go to Heaven in Dark Side of the Moon, Castiel asks them to look for Joshua, as he may know where God is. They find Joshua and find out that God knows about Earth's problems and simply doesn't care. This hurts Castiel, who renounces his faith in God and disappears.
Following that, in 99 Problems, Castiel arrives on the scene drunk, short tempered, and bitter. He and Dean later have a heart-to-heart about poor fathers.
In Point of No Return, Dean attempts to say yes to Michael, which horrifies and enrages Castiel. They lock Dean in the panic room of Bobby's basement to stop him from leaving. The feelings of betrayal come to a head when Dean escapes Bobby's home by banishing Castiel and attempts to contact the angels. Castiel appears and beats Dean within an inch of his life, venting his frustration and hurt. He later goes on a suicide mission, stating that he would rather die than watch Dean crumble and fail.
Castiel later returns in Two Minutes to Midnight and apologizes to Dean for not having more faith in him. Dean forgives Cas, and they reconcile. However, Castiel admits that, technically, he is human, having depleted his "batteries" during his suicide mission. Despite this, Castiel still comes to Dean and Sam's rescue and cuts off Pestilence's finger.In Swan Song, Castiel is shockingly human, displaying more emotion than ever. He appears during the fight between Michael and Lucifer, distracting them by throwing a molotov cocktail of holy fire at Michael. This allows Dean to try and get through to Sam, though it ends with an offended Lucifer causing Castiel to explode.
The angel is brought back after the battle, "new and improved", and heals Dean and brings back Bobby. Dean suggests that God wants Castiel to be the new leader of Heaven, though they part ways on a tense note.
- "Dean and I do share a more profound bond. I wasn't going to mention it."
Castiel comes when Dean calls him in The Third Man. He mentions in this episode that he has more of a bond with Dean than Sam. Castiel helps Dean figure out it is the Staff of Moses doing the killing and the trail leads to a rogue angel and friend of Castiel, Balthazar. Castiel also mentions that he needs the stolen weapons of Heaven back due to a civil war in heaven against the archangel Raphael.
Dean calls Castiel again when he's worried about Sam, but Castiel refused to answer unless it was connected to the he and dean had which angered Dean. When Castiel does show up, he dismisses Dean's theory that Lucifer still inside Sam. Castiel promises Dean to make some inquiries after telling him that he, Castiel, doesn't answer Dean's prayers when they're connected to Sam because he doesn't know how to help.
Dean later calls Castiel to check what wrong with Sam (Family Matters). Castiel reaches into Sam, and discovers that he doesn't have a soul, and explains that whoever brought Sam back left Sam's soul behind in the cage with Michael and Lucifer. When Dean questions whether soulless Sam is even still "Sam", Castiel admits that that's a good question.In Caged Heat, Castiel exhibits more human urges, inadvertently watching porn, and later passionately kissing Meg, both to Dean's discomfort. Castiel warns Dean that bringing Sam's soul back could permanently damage the younger Winchester psychologically, but Dean remains firm on retrieving the soul. Castiel is banished with a sigil when they lay siege to Crowley's warehouse, but later returns with Crowley's bones, which he promptly incinerates when Crowley admits he can't retrieve Sam's soul from the cage. Later, when Castiel admits to Dean that he is on the losing side of the civil war in Heaven, Dean assures his friend that if he needs help, all he has to do is ask.
When Sam gets his soul back, Dean calls Castiel to check on him. When Dean questioned Castiel on whether or not Sam will wake up, Castiel is curt with him, and berates Dean for not listening to him. When Dean reacts defensively, Castiel angrily tells him that Sam's soul felt "as if it was skinned alive", and tells Dean that if he wanted to kill his brother, he should have done it outright, making his stance on the matter clear.
When Castiel and Balthazar go back in time to stop the Titanic from sinking, Atropos, one of the three Fates, forces Castiel to capitulate and fix the timeline by threatening the Winchesters. He doesn't tell Dean or Sam the real reason for going back in time; while he really sent Balthazar so that they would have more souls for the war, he allows them to believe that Balthazar simply didn't like the movie, or Celine Dion.
Later, the Winchesters find a way to kill Eve, with the ashes of a phoenix. However, their call for Cas is answered by his lieutenant, Rachel, who promptly looses her temper with them after they insist on speaking with Castiel. Despite her passionate words on his behalf, Castiel appears and dismisses her, much to her chagrin. He agrees to help them go back to the Wild West, and is the first to question Dean's choice of dress, asking if wearing a "blanket" was customary.
When the Winchester's search for Eve rapidly proves fruitless, Bobby suggests that Dean call Castiel. However, Castiel admits that he's had no luck either. When the Winchesters decide to track down a monster that is loyal to the cause, Castiel finds Lenore, a vampire that has had run-ins with the Winchesters before. After she tells them what she knows, she begs them to kill her, the call of the Mother forcing monsters to give into their baser natures. While the Winchesters are both reluctant, Castiel obliges. When they go to the town Lenore told them the Mother was in, Castiel is made powerless by her, much to Dean's irritation.In The Man Who Would Be King, Castiel's betrayal is slowly becoming known though Dean does not want to believe it, and desperately remains loyal to his friend. In the beginning prequel part of the episode, Castiel attempts to explain freedom to the angels (in hindsight, he describes the experience as being comparable to teaching poetry to fish, and cynically states that he should have told them that "Freedom is a length of rope. God wants you to hang yourself with it"). Raphael is less than enthused, and demands that Castiel show his support, though Castiel refuses when Raphael announces his intent to restart the Apocalypse. Castiel almost goes to Dean for help, but ultimately decides not to drag his friend into the mess, rationalizing that Dean has been through too much already. Crowley appears and, playing on the angel's new sense of pride, manages to strike a deal with Castiel: his help, and 50,000 souls upfront, in exchange for half the souls of Purgatory. Castiel agrees out of desperation, and while Crowley insists that keeping the Winchesters alive is dangerous, Castiel refuses to kill them, still considering himself their guardian angel. However, during this time, Castiel takes to spying on the Winchesters and Bobby, and later betrays this fact by referencing part of a conversation he'd overheard. This leads the others to realize that he is not to be trusted, and they capture him in a circle of holy fire. Dean takes it the hardest. Later, Castiel goes to Bobby's in an attempt to explain his actions, but refuses to back down, even when Dean threatens to fight back. Despite this, Castiel still helps Dean in Let It Bleed. When Dean is about to be killed by a demon he's interrogating, Castiel steps in and saves him. Dean is still hurt by Castiel's betrayal, and reacts with hostility. Castiel tells Dean that he too considers them to be family, and tells Dean that after all he, Castiel, has done for the Winchesters, Dean should trust him. Even when Dean says he can't, Castiel tells him that he will find Lisa and Ben, who had been kidnapped by Crowley. They part on a hostile note, with Dean telling Castiel that he doesn't want his help. Later, Castiel comes by Lisa's hospital room, and despite Dean's exhausted hostility, heals Lisa without prompting. Dean, though immensely grateful, states that it doesn't change the situation, a statement that Castiel regretfully agrees with. Dean asks for one more favor, which Castiel grants: the angel erases Ben and Lisa's memories of Dean.
Castiel later appears before Dean in The Man Who Knew Too Much. Dean is angry at Castiel when he appears after killing Dr. Visyak. Castiel tells Dean he no longer cares what he thinks, and is tired of getting his approval, but promises that if Dean doesn't fight anymore, Sam will be alright in the end. In an apparent attempt to distract Dean, Castiel breaks down the mental wall that stopped Sam from remembering his year without a soul or his soul's time in Hell.After Castiel absorbs the souls of Purgatory, Castiel tells Dean despite his doubts, Castiel was right in what he did. Dean tries to talk to Castiel to releasing them. Dean finishes his emotional plea by saying how Castiel was family once and if that still has any value to Cas, he will listen to Dean. Castiel mentions that Dean is afraid of his power (immediately implying that he isn't going to listen to Dean's plea), which is why Dean is being nice to Castiel.
Castiel informs Dean that he is no longer his family, that they never were family, and that he has no family. He proclaims himself to be the new, better God, and demands that they bow and proclaim loyalty and love, or be destroyed.
- "Dean." "You want something else?" "No, I feel regret. About you and what I did to Sam. "Yeah, well you should."
- —Castiel and Dean[src]
After Castiel's betrayal, both sides are hurt by each other. Castiel spares Dean, and leaves. Dean realizing he can't fight againist Castiel, gives up until an idea to bind death comes up. Dean and the other summon and bind Death to kill Castiel. When Castiel appears, Dean quickly tells Death to kill Cas, but Death is freed. Dean has given up on Castiel, until Cas comes asking for help. Dean rushes to Castiel's aid. While working, Castiel apologizes to Dean for what he's done, and promises to make it up to Dean. As the door opens to Purgatory, Castiel falls down, and Dean rushes to help him stand. Castiel soon releases all the souls back into Purgatory.
However, the Leviathans stayed in Castiel and soon took over. Castiel's vessel wasn't able to contain them for very long and began melting black ooze. The Leviathans headed towards the municipal water supply, and disappeared in the water. The only thing left behind was Castiel's trenchcoat. Dean is upset at his friend's loss. In Shut Up, Dr. Phil, Dean has nightmares of Castiel's death, showing that Dean still feels the loss of his good friend.
Much to his surprise, Dean finds Castiel again and is shocked to see him alive. In The Born-Again Identity, Dean finds Castiel, now going by Emanuel, married and has no memories of his past life. Putting his anger aside, Dean asks Cas to heal Sam. On the way to the hospital, Dean and Castiel talk, and Dean mentions about how his "friend" betrayed him. Castiel doesn't catch on to this, and tells Dean that he's not a machine. When Meg tags along, Dean fears telling Castiel the truth in fears that Cas won't help Sam.At the hospital, many demons block their path. Castiel overhears Dean and Meg talking, and walks over. Meg tells Castiel hes an angel, and Dean backs this up. As Castiel smites the demons, he begins to remember. After all the demons are gone, Castiel attempts to leave saying he shouldn't be here after what he did. Desperate to help Sam, Dean tries to defend Castiel's previous actions, but Castiel shoots it down. Castiel wonders out loud why he lived. Dean resorts to Castiel, to fix things, and gives back Castiel his trenchcoat. Castiel saves Sam from a demon, but tells Dean he is unable to fix Sam's mind. In order to redeem himself, Castiel takes on Sam's memories of hell. Unable to help Castiel, Dean leaves him in the mental ward of the hospital. Dean is still concerned for Castiel and calls to check in on Castiel with Meg. In Reading Is Fundamental, Dean gets word that Castiel is awake and heads over. When over, Castiel warmly greets the both of them, like "Hello Dean. Sam.". Meg and the boys start arguing, and he disappears with, "Don't like conflict". Dean finds Castiel calmly seated, and together they play 'Sorry'. As they play, Dean gets increasingly frustrated with Cas and pushes the board away while shouting "You're not sorry, you're playing Sorry!" Dean still can't forgive Castiel for what he did.
In Survival of the Fittest, Dean is showing signs of forgiving Castiel and taking in Castiel's new mental state. When they notice that Dick has multiplied, Meg points out that they need Castiel. Dean gets angry when Castiel says he doesn't want to get involved and he angirly points out that they are cleaning up Castiel's mess. Castiel changes his mind when see Dean say goodbye to Bobby. After, Dean asks Castiel to take him to where they are hiding the Impala. Castiel tells Dean hes not good luck and probably get everyone killed. Dean points out that he rather have Cas on his side than not at all. Castiel notices that it sounds like Dean is forgiving him and agrees to help, possibly out of loyalty to Dean after Dean says he's probably going to die in the attack.
Dean and Castiel begin looking for the real Dick Roman. Together they are able to find the real one and stab him with the bone fragment. The first is a fake, so while Dick is occupied, Castiel grabs him from behind so Dean can stab him with the real one. This causes Dick to explode, sending Dean and Castiel to Purgatory. Castiel wakes Dean up and tells Dean where they are. As the monsters come close, Dean notices that he is alone due to Castiel teleporting away.
- "I have a price on my head, and I've been trying to stay one step ahead of them to keep them away from you"".Cas, buddy, I need you. And if Leviathan want to take a shot at us, let them. We ganked those bitches once before, we can do it again."
- —Castiel and Dean[src]
While in Purgatory after Castiel's disappearance, Dean was relentless in finding his wherabouts. In What's Up, Tiger Mommy? Dean finds Castiel near a river and is happy to see his old friend who is now sane again. Castiel reveals that he did abandon Dean, but to protect him from the Leviathans. Dean convinces Castiel to join him and Benny in their quest to get out, and he refuses Castiel's repeated pleas througout the journey to leave him be as he is drawing monsters to them due to being a Seraph. When Benny saves Castiel from a Leviathan, this seems to increase Dean's trust in the vampire, that he would help Castiel out despite all of his arguments against Castiel being with them. Castiel and Dean later fight two Leviathans together with Castiel helping Dean to kill one. Dean gets out of Purgatory through the portal they find, but Castiel stays behind, believing that staying there will be pennance for his sins. Dean remembers it as losing his grip on the angel and carries a lot of guilt for this. He later tells Sam that Castiel didn't make it, but only says that it got hairy near the end and that Castiel "just let go," refusing to elaborate.After Castiel's return in A Little Slice of Kevin, Dean is happy to see him, but is suspisious of his return, knowing that Castiel was in no shape to escape on his own. He later tries to asuge his guilt by talking to Castiel and Castiel is shocked that Dean blames himself for what happened. Dean and Castiel fight their way through Crowley's warehouse together, but Castiel leaves Dean behind to fight Crowley himself despite being in a weakened state from Purgatory that only gets worse when he uses his powers. Castiel later uses his powers to show Dean the truth about his staying in Purgatory, stunning Dean. When Naomi asks him to report on Sam and Dean, Castiel refuses but has no choice and later agrees to join Sam and Dean in their quest to get the second half of The Word of God from Crowley.
In Hunteri Heroici, Dean is still confused how Castiel got out of Purgatory and asks Castiel how hes feeling. Castiel responds that he's fine and doesn't feel any effects from his escape from Purgatory. Castiel also confides in Dean his fear that if he returns to Heaven, he will kill himself out of guilt after seeing what he has wrought there. While Dean is initially skeptical about Castiel becoming a hunter, after he proves vital to solving the case, Dean accepts it, even agreeing to let him ride "shotgun" in the Impala, something he'd previously refused.
In Torn and Frayed, Castiel goes to Dean for help in rescuing Samandriel. With Dean's help, Castiel manages to locate Samandriel, but refuses to listen to Dean when he tells him not to bring in Sam to help. When he brings Sam, Castiel yells at them to "stow their crap." Later, Dean realizes something is wrong after Castiel kills Samandriel and from the way he is acting.
In Remember the Titans, Dean prays to Castiel earnestly, practicaly begging for Castiel to look out for Sam who is clearly not doing well in his trials to close the gates of Hell forever. Despite Dean's pleas, Castiel does not respond or appear.
In Goodbye Stranger, Castiel is now so indoctrinated to Naomi's control that he has no problem with ruthlessly killing a copy of Dean and is shown to have killed hundreds of them in order to desensitise him. However, this may be as he knew they weren't really Dean. When he meets up with Sam and Dean again, Castiel admits that he heard Dean's prayer but is not back because of that and under Naomi's control, lies to Dean about why he is there and activly covers up what he is really doing. Castiel is the one who finally tells Dean that there is indeed something seriously wrong with Sam, explaning that Sam is damaged down to the subatomic level, something even Castiel can't fix. Castiel is forced to point out the angel tablet to Dean as it is angel-proofed and is ordered to kill him by Naomi. Castiel attacks Dean completly out of his control as despite his indoctrination, Castiel himself still refuses to harm the real Dean. Dean pleads with Castiel to stop and finally breaks through to him by reminding him that he is family. Castiel stops his attack, choosing Sam and Dean over Naomi and Heaven and when he picks up the angel tablet, he is freed from Naomi's control fully. Castiel explains to Dean what happened and heals him, though Dean flinches when he reaches to do so, expecting another attack. Castiel leaves with the tablet, saying he must protect it from Dean as well for a reason he doesn't explain.
Naomi later visits Dean and, in an attempt to manipulate him, plays on his love for Castiel and suggests perhaps Castiel does not feel as strongly in return as he is missing. It is revealed Dean removed any angel proofing sigils from the bunker so Castiel could find and return to he and Sam.
In Clip Show, after reuniting with a severely wounded Castiel, Dean is angry with him and refuses to forgive Castiel for abandoning him again and not trusting him to the point that he fled with the angel tablet and got it stolen by Crowley. Castiel is noticeably hurt by Dean's anger, but Dean appears to feel Castiel should feel guilty for his constant disappearances. Though notably he insists Castiel stay behind to heal, which suggests he was working through his anger. In an attempt to make up with Dean, Castiel awkwardly shops for supplies while he is gone, buying Dean's favorite porn and trying to get him pie. When Castiel learns that there is no pie, he angrily grabs the minimart clerk, insisting that he needs the pie, but is interrupted by Metatron. As Castiel teams up with Metatron to close the gates of Heaven, he never returns with the supplies and Dean believes he has abandoned them again.
In Sacrifice, after Metatron is captured by Naomi, Castiel approaches Dean for help with the trials to seal Heaven. Dean is reluctant to leave Sam as he is so close to completing the Hell trials and suspicious of Metatron, but agrees after Sam insists. Dean helps with locating the third trial by bringing the angel tablet he has retrieved from Crowley to Kevin, but is shocked by Castiel's strong-arm tactics with Kevin. Dean and Castiel share a drink in a bar whilst waiting for a Cupid to show up. They discuss their possible fates and Castiel admits he may be killed for turning his back on heaven and attempting to shut the gates. When confronting the Cupid for her bow, Dean keeps Castiel from attacking her and they are able to simply convince her to give it to them by telling her about the situation in Heaven and promising to right it. When Naomi arrives and wants to talk, Dean is able to convince Castiel to hear her out and not attack outright and while Dean believes her, Castiel doesn't and remains angry that she forced him under her control for so long, and tried to make him harm Dean. At Dean's request, Castiel transports him back to Sam, but he refuses to stick around and help, annoying Dean.
- "Dean, you know I always appreciate our talks, and our time together."
In I Think I'm Gonna Like It Here Dean, not knowing about Castiel being human after Metatron took his grace, prays to Castiel but as he does not respond, Dean reacts angry and desperate and expands his prayer to all angels because he really needs someone to heal Sam being about to die after almost finishing the trials to shut down hell. In the hospital Dean receives a phone call from Castiel telling him of his new humanity and asking him about recent events. When Dean tells him about Ezekiel, Castiel confirms that he is trustworthy and even calls him a good soldier. Castiel also tells Dean about meeting Hael but Dean states that Castiel should trust nobody because the angels are trying to find Castiel and they are "pissed". He convinces Castiel of leaving Hael on her own and coming to the bunker as soon as possible.
In I'm No Angel days have passed since Dean told Castiel to come to the bunker but the former angel still has not arrived. Sam just tells Dean not to worry because Castiel is human now and, as a consequence, needs more time to travel when Ezekiel takes over and informs Dean about the angels organizing and Castiel being hunted. Because of this Dean and Sam are trying to find Castiel before the angels do. After learning that rogue Reapers are hunting Castiel, Dean calls on Ezekiel to find him, despite knowing its dangerous for the angel to be in control. Dean arrives in time to see the Reaper possessing April Kelly kill Castiel with an Angel Blade. Dean manages to kill April with the same blade she killed Castiel with, but it is too late because Castiel is already dead. Just after Dean realized this and starts to show emotions, Ezekiel takes over Sam's body again and revives Castiel without any hesitation. Back in the bunker Castiel tells Sam and Dean about having sex with April who are very, very surprised by this and Dean even chokes on his burrito. As Castiel leaves the room Ezekiel shows up again and forbids Dean to let Castiel stay and if he does not tell him to leave, Ezekiel will leave Sam's body, causing him to die. Dean having no other choice informs Castiel that he can not stay and Castiel is only able to answer with an incredibly hurt look.
In Heaven Can't Wait, after getting wind of a possible case, Castiel calls Dean who comes to help and also to get away from research and to spend more time with him.. Feeling guilty for kicking him out of the bunker, Dean avoids Castiel at first, but eventually comes to him and recruits him as his partner in hunting for this hunt. Together they determine they are dealing with an angel and when Castiel goes to what he thought was a date, Dean gives him hot dating advice. Later, Dean realizes that Castiel is in trouble after recognizing a truck belonging to the vessel of the angel, Ephraim, as one he'd seen outside the house Castiel went to and he rushes to Castiel's aid. Though Dean is unable to defeat Ephraim, he tosses Castiel an Angel Blade as Ephraim is about to kill him, allowing Castiel to kill Ephraim and saving his life. Dean later returns Castiel to his new human life at his request and apologizes for kicking him out, but keeps the knowledge of the fact that Metatron's spell can't be reversed from him as he knows Castiel will feel immensely guilty for it due to his role in the expelling of the angels.
Dean gets sent forward in time by Zachariah in The End. There Deans finds a "zombieland" like world. Dean goes looking for familiar faces. Then Dean finds the rebel camps where he finds himself and Castiel. Although Castiel is not what he used to be. Dean is shocked by how loose Castiel is (Dean walks on Castiel preparing to have an orgy). Castiel also comments how he likes past Dean better. On the way to the battle field, Dean asks what happened to Castiel. Castiel replies life and the fact he's no longer an angel. When Castiel (past one) saves Dean, Dean tells Cas "Don't ever change"