At the beginning of Season 3, Caroline and Tyler started a romantic relationship. It was then affected when Tyler was turned into a Hybrid by Klaus, which created a sire bond that Caroline didn't approve of.
In Our Town, Klaus tells Tyler that he wants him bite to Caroline, him flatly refused but Tyler accidentally bites to Caroline.
Tyler going for help to Klaus and he decides to save her. Klaus went to house of Caroline to save her and after have a conversation, she finished drinking the blood of him.
Tyler is forced to make a decision on whether he wants his freedom at the cost of having to go through extreme pain to break his sire bond to Klaus. He leaves Mystic Falls, after hurting Caroline caused by his sire.
In Dangerous Liaisons, Klaus then invites Caroline to the ball, and continues to persuade her although she does not reciprocate those feelings, claiming she is spoken for by Tyler. Caroline speaks with Klaus and she tells him that let to Tyler free. They discuss and Caroline ends up leaving the house of Klaus. When she arrives home, she finds a drawing Klaus sketched for her where he thanks her for her honesty.
Later, Klaus expressed a romantic interest in Caroline, who, despite his charm, turned him down several times.
In Heart of Darkness, Tyler has successfully broken the sire bond and returns to Mystic Falls but spots Klaus´ drawing. Seemingly confused, Tyler questions Caroline, asking her why she kept it. Jealous that something might have happened between Klaus and Caroline while he was gone, Tyler leaves Caroline's house.
In Do Not Go Gentle, Caroline plays a big part in preparing the Decade Dance. Tyler shows up at the dance determined to make up Caroline's mind about him, and he and Caroline dance together until Klaus shows up. Klaus asks Caroline to dance with him. At first she rejects him but says yes after Tyler agrees to it. While they danced, Klaus tells her he's leaving the next day. Caroline responses with anything but relief. He says he would invite her to go with him but he knows she's not ready yet. He tells her that he'll show her "what the world has to offer" if she shows up on his doorstep one day. Caroline just scoffs, hurting Klaus's feelings. Before Klaus leaves the dance, he promises Caroline that she'll soon be bored with her "small-town boy" and her "small-town life" and that it won't be enough for her. Caroline watches Klaus leave, with an unquestioned look on her face. Later in the episode, Caroline informs Tyler that he does not have to worry about Klaus, and that she loves him.
"You mark my words. A small town boy, a small town life, it won't be enough for you. "
In The Departed, Tyler and Caroline are informed by their mothers that Alaric outed who they were to the council, and that they had to run before they came after them. They agree to run away together, and meet in the cellar in two hours after Caroline helps Elena after she suffered from concussion. Later, Klaus is staked by Alaric, and it is then assumed that Katherine, Damon, Stefan, Caroline, Tyler and Abby will die. However, Bonnie took action before he was staked, and told Tyler that if Klaus possessed him, and if [Klaus's body] was staked, that the others wouldn't die, only Tyler would. He agreed, wanting to keep everyone else alive.
After Klaus was killed, Caroline races to the cellar, wanting to catch Tyler before he died. She is then despaired when she believes he has already died. However Klaus (in Tyler's body) comes in and tells Caroline he was just with Bonnie. She then informs him that Klaus is dead. Klaus (although unkown to Caroline that it is him) tell him that she's going to be fine. He tells her he's a lost cause, but she's strong and has a beautiful future. They hug and share a kiss, although Caroline believes it is Tyler she is actually kissing. He fakes coughing, and tells her to leave. After she refuses, he transforms, and tells her to leave or he'll make her. She reluctantly leaves after he tells her to go.
In Growing Pains, Caroline, who was supposed to be away from Mystic Falls but stuck around because she didn't know where to go without Tyler, gets captured by Pastor Young and the deputies. Klaus, who was in Tyler's body rescues her, and she is overjoyed and surprised when she sees that "Tyler" is alive. Caroline and Tyler/Klaus are later shown making out in the woods, right before Caroline discovers that the person she thought was Tyler is actually Klaus and slaps him, as she was very close to having sex with him.
Later Caroline and Tyler/Klaus turn to Bonnie and ask her to put Tyler back in his body, which she does.In The Rager, Klaus visits Tyler's house and meets Hayley, a werewolf from Tyler's past. While speaking to Hayley, Klaus overhears Tyler telling Caroline to go to Rebekah's party, and assumes that something has happened between Tyler and Hayley. When Tyler walks into his dad's old office, Klaus is sitting in the chair. Klaus tells Tyler that he thinks when Tyler went to go break his sire bond he met Hayley and they shared a passionate moment. Tyler gets upset and shouts at Klaus to stop. Klaus then says angrily, "And Caroline has no idea." Tyler stares at Klaus with shock and Klaus scoffs, shaking his head and giving Tyler a look before going to answer Tyler's cell phone.
"You went off to the Appalachians to break my sire bond. There you met a pack of werewolves, among them was a girl. She was gorgeous with the same animal instincts as you. Emotions ran high and ambitions ran low. In a moment of weakness the thick sexual tension became something much more real. And Caroline has no idea."
In We All Go A Little Mad Sometimes, Caroline arrives at Tyler's house with a box of Tyler's things, interrupting a heated discussion between Tyler, Hayley and Klaus. While this is a fake display to legitimize a break-up between her and Tyler, Klaus believes it. Giving Caroline, Tyler, and Hayley space, Klaus leaves with two other hybrids.
In My Brother's Keeper, Caroline is at the Lockwood mansion helping to organize the Miss Mystic Falls Pageant for the following day. While Caroline is working, Klaus arrives to inquire about the date she promised him. Caroline is initially opposed to Klaus accompanying her to the pageant as her date, but she relents after Klaus reminds her of Tyler's indiscretions with Hayley.
Later as Klaus prepares to uncork the champagne, Caroline asks him if he would ever take the cure. Klaus replies by wondering aloud why he would want to cure himself of being the most powerful creature on the planet. Unsatisfied, Caroline confirms his response by asking again. He evades her question by asking her if she would take the cure. With Tyler watching from a distance, Klaus recalls that life used to be a lot easier. They have fun on your date.
While Tyler listens into their conversation, Klaus admits to Caroline that there was one time when he thought about being human. He recalls a trek in the Andes where he encountered a hummingbird hovering in front of him. He noted the bird's heart beating rapidly and appreciated how hard the bird had to work in order to survive each day and how satisfying that must be. Tyler are really jealous and tells to Hayley that they must to Klaus end as quickly as possible.
In Into the Wild, Tyler finds Klaus, who has been trapped by magical barriers Bonnie made, in the Gilbert house, where Elena and Jeremy had recently killed Klaus' brother, Kol. Tyler was gloating to Klaus about how his friends were going to find the cure and when they did, he'd turn Klaus mortal and figure out which way would be most fun to kill him. Klaus tried to plant the idea that if he is cured, his whole bloodline would be cured too, but Tyler disagreed.
When Caroline arrives in the Gilbert house surprised to find Tyler still there and Klaus still locked in the family room. Klaus greets Caroline unsurely which she responds to dismissively. Caroline then urges Tyler to come home to avoid stooping to Klaus's level. Tyler refuses, preferring to revel in Klaus's misery until he can kill him himself. Caroline compromises by suggesting Tyler gloats and multi-tasks by helping to clean Elena's house. They start by covering Kol's body and Klaus responds emotionally. Klaus reasons that now that his brother Kol is dead along with Tyler's mother, Carol, that they are now even.
But Caroline, remembering Aunt Jenna was also among Klaus’ death toll, said she’d never help him and that he wasn't even worth the calories she burns talking to him. That’s when Klaus impaled her with the other end of a lamp, pulled her to him, and bit her. “Now that was definitely worth the calories,” Klaus says after he drops her body on the floor with Tyler looking surprised.
Later, Caroline is shown panicking over what Klaus as done as Tyler helps her down onto the Gilbert's living room sofa, while Klaus stares away from the unfolding situation. Tyler tries to calm Caroline down by assuring her that he'll fix things. Tyler confronts Klaus, reminding him that Caroline will die if he doesn't give her his blood. Klaus seems sarcastically receptive, biting his wrist and extending it to Tyler. He asks Tyler to beg him to save her life. Tyler scoffs at Klaus's attempt to underscore how powerless he is compared to him. Tyler relents and begs Klaus to save Caroline. Klaus states that it would be pathetic of him to help since in a previous conversation Tyler revealed that once Klaus was forcibly given the cure that he would kill him. Tyler responds by offering to be Klaus's slave again in exchange for healing Caroline. Klaus refuses him. Obviously hurt, Caroline asks Tyler to help her leave the room as she is unable to look at Klaus.
The next day Caroline is in the Elena's room with Tyler, after a conversation he asks if she trusts in him. The leads to the room with Klaus and tells him that if he wants to let her die well but that would have to see it with your own eyes, Tyler will goes leaving to Caroline on the floor with Klaus looking her.
Caroline asks how Klaus could do something like this to Tyler, to his mom, and to her. He responds dismissively, citing boredom as a reason. Caroline does not believe him. Klaus then suggests that his actions are motivated by the fact that he's pure evil. Caroline counters this explanation by concluding that Klaus does what he does, because he's hurt. This garners Klaus's attention. She continues by suggesting that since Klaus is capable of hurting there is a part of him that is human. Surprised by her words given all that he's done, he moves closer to her and wonders how Caroline could think that.
She confesses that she's seen his humanity; that she's found herself wishing she could forget all of his horrible actions. Klaus concludes presumptuously that she can't, faltering slightly as he seems to ask her if she could forget. Caroline does not answer him directly. Instead, she points out that she knows that he is in love with her and that anyone capable of love is capable of being saved. Clearly affected by her words, Klaus ignores her claims by reducing her words to the product of a hallucination. With her death not far off, she concedes that she'll never know. At this point, her body appears to be succumbing more rapidly to Klaus's bite. Panicked, Klaus repeats her name a few times, but she is unresponsive. Conflicted, Klaus weighs his options before ultimately deciding to heal her. He props her up as he moves in behind her on the couch. He bites his wrist and offers it to her. She responds to his blood, holding his forearm and hand as she drinks.
In Down the Rabbit Hole, Caroline and Tyler would have found the sword in Klaus' attic. The handle is a cryptex ("I've seen the Da Vinci Code," Caroline said), so they basically had to twist parts and read Aramaic, which of course Klaus knew. There's only one dose of the cure. Klaus, who'd wisely decided that he could help Caroline and Tyler read the cryptex and keep that important information to himself, shouted it out to Rebekah when Caroline phoned her to say they were emailing the translation and directions.
Later, Tyker wanted to get out of town, knowing Klaus would start with him. Caroline begged him to let her try to fix things with Klaus because she didn’t want to say goodbye to him again.
Caroline talks with Klaus for mercy for Tyler, Klaus refuses at first but then Caroline is convincing. When Caroline is going to go Klaus tells to Caroline that mercy to Tyler is for she, who must leave immediately of MF because only give you an advantage before killing him, Caroline looks disappointed.
Caroline said a tearful goodbye to Tyler. They’re immortal, he reminded her. “This isn’t goodbye, this is until we find a way,” he said. Also simultaneously heartwarming and heartbreaking was her response: She told Tyler if they couldn’t find a way, he had to promise he’d live a full, happy life without her and never think of her again. For her sake, he said it. They kissed. He slowly walked away. And Caroline sat there crying.
Later, Klaus walked out of Elena's house. He told Caroline he assumed he was free because something had happened to Bonnie. He also said he’d never hurt Caroline, and that he’d shown kindness, forgiveness, and pity -- for her.
In Because the Night, Klaus asks to Caroline if knows where Tyler is to which she responds by informing Klaus that he's not with her and has surrendered the deed to his house to Matt Donovan. Klaus steps forward and points out that it was Tyler's intent to kill him and that it's unfair of Caroline to hate him for driving him away in response. Caroline disagrees, suggesting that she does hate him before telling him to go away.
In American Gothic, After that Klaus has been allegedly stabbed with white oak stake for Silas, he calls for help to Caroline. At first Caroline refuses, remember him what he did to Tyler and Carol but Klaus]] reminded her/us, if he dies, Caroline and everyone she knows dies. She had to help. He told her she’d need to cut the stake out of him.
After discussing the freedom of Tyler, Caroline ends up helping him. Later, when Caroline is going to go, Klaus thanked her for her help, she poked his chest when she told him if he needs anything else not to call her because she has a prom to plan. "Friends?" he asked, She asked if he was letting Tyler come back to town. He didn’t answer, at first. But he did then say she might have noticed that he’s not exactly scouring the earth for Tyler and then she leaves, smiling.
In Pictures of You, Tyler returns to Mystic Falls to see Caroline the day of prom. After sharing a dance together Tyler say goodbye to Caroline.
Klaus was also out of the Lockwood mansion after Tyler showed up, he asked Tyler if it worth it seeing Caroline's smile but Tyler did not answer anything and then he gave five seconds to Tyler to leave before Klaus kills him. After Tyler goes, Klaus look at the mansion with a regretable look, knowing that Caroline is inside.
In Graduation (Episode), In the evening Klaus returns with Caroline and shows the invitation that she had sent for him. Klaus says he has a gift for her. He thought of giving her a first-class ticket to New Orleans, but he decided that he would give her something he knows she will accept and is Tyler's return to Mystic Falls. He then says to her "He's your first love, I intend to be your last however long it takes" and then kisses her on the cheek, the two leave the school together.
Tyler/Klaus: There’s no point. I’m a lost cause, but you’re strong and you have a beautiful future ahead of you. And when you make it through this, just tell my mother I left town like I was supposed to, okay?
Klaus to Tyler: You went off to the Appalachians to break my sire bond. There, you met a pack of werewolves, begged them for help. Among them was a girl. She was gorgeous, with the same animal instincts as you. Emotions ran high. Inhibition ran low. Then, in the moment of weakness, the thick sexual tension became something much more real. And Caroline has no idea.
In the books, Caroline has a temporary alliance with Tyler to harm the relationship of Elena and Stefan. After the arrival of Klaus, Caroline is kidnapped by Klaus, and Tyler is allied to the Old One in order to destroy Stefan.
Klaus, Caroline and Tyler are the second main love triangle of series.
Klaus leaves Mystic Falls but he told Caroline that he would wait as long as necessary for her.