Plot

Kabir and Naina bond during a trekking trip. Before Naina can express herself, Kabir leaves India to pursue his career. They meet again years later, but he still cherishes his dreams more than bonds.

Yeh Jawaani Hai Deewani is the story of the relationship between two characters, Bunny (Ranbir Kapoor) & Naina (Deepika Padukone), at two separate but defining times in their lives... first, when they are just out of college and standing on the crossroads of multiple decisions that will shape who and what they become... and then later on, in their late-twenties when they meet again, holding on to certain fulfilled and certain unfulfilled dreams, at a crossroads of another nature this time... how these two characters affect, change, befriend and eventually fall in love with each other is the journey the film aspires to take us on..—Eros International

Kabir Thapar / Bunny (Ranbir Kapoor) is a carefree boy whose dream is to roam around the world, and he doesn't believe in the marital bond. He lives with his father Sanjay (Farukh Sheikh) and stepmother Shivani (Tanvi Azmi). Kabir wants to live life on his own terms and doesn't share any kind of emotional bond with his stepmother.

Avi (Aditya Roy Kapoor) and Aditi (Kalki Koechlin) are his best friends. Aditi loves Avi but did not have the courage to reveal her feelings to him. Avi teases Aditi that she is a lesbian. Avi is a compulsive gambler and has lost all his pocket money betting on a cricket match. Bunny is a charmer whose dream is to wander and discover the world; he has no interest in settling down. Avi is a playboy only interested in alcohol and betting.

Those three friends plan to visit Manali. Naina (Deepika Padukone) is a medical student and was classmates of Bunny & Aditi when they were in school. Bunny was a last bench student, while Naina was a topper throughout. She meets Aditi by chance at a supermarket & learns she is going to Manali on a hiking trip. She wanted a break, so she decided to join the trip with those three friends. Naina lives with her overbearing mother Simran (Dolly Ahluwalia) & wimp father (Punya Darshan Gupta).

Kabir funds Avi's trip via his savings. In the group with them is Lara (Evelyn Sharma), who has the hots for Kabir. Kabir also flirts shamelessly with Lara. During the hike, Naina renews her friendship with Aditi and her other former classmates.

Naina is the outcast in the group. She realizes that in the drinking game, she is the only one who has not done any wild things in life. Naina and Kabir share many adventures, including outrunning local hooligans when they get into a scuffle with Aditi and Avi, sharing a Holi party together, climbing a haunted mountain together and sharing campfires. Bunny helps Naina open up and express her own personality. During the journey Naina falls in love with Bunny, even if there is no similarity between them. Naina also realizes that Aditi is in love with Avi. Aditi becomes jealous as Avi flirts with another trekker.

One day Naina tries to express her love in front of Bunny, but at that time it was revealed that he had got scholarship at the Northwestern University, Chicago and reveals to the rest of the group that he is leaving India in three weeks. As Bunny is so fond of exploring, he decides not to pass this opportunity, so he goes to Chicago. Avi is angry with Bunny for applying to the scholarship without letting him know. Adi tells him he should go, explaining that they are all growing up and that it is time to become adults. Naina never reveals her love to Bunny as she knows that Bunny desires nothing but freedom in his life, so she decides to bury her feelings. Naina realizes that love and marriage have no part in Bunny's plans.

Bunny travels the world as a National Geographic photographer. He loves his life. But he lost his father in those years. He wasn't even able to attend the funeral as he was away hiking at the time, with no mobile coverage. By the time he came to civilization, the last rites had been performed. With Bunny's show coming to an end, he receives an offer to become a host for a new travel show, which he accepts.

Moving around too frequently to be reached by post, he receives a virtual wedding invitation video from Aditi; she is marrying a nerdy, wealthy engineer, Taran Khanna. Bunny is invited to Udaipur for her destination wedding.

After eight years Bunny returns from Chicago, when asked by Aditi to attend her wedding to Taran (Kunaal Roy Kapur) in Udaipur. Naina and Avi are in attendance as well. Naina has finished medical school and is now working in a clinic.

Bunny has to work through his issues with Avi as he is super angry that Bunny never remained in touch over the years. Avi started a bar and that is on the verge of being shut down. Avi does not consider Bunny his friend anymore. Bunny notices that Avi is trying to earn some money by gambling on cards with the wedding guests, but he keeps on losing.

Avi says that he had no expectations from Bunny. Even Aditi had no expectations that Bunny would turn up at her wedding, as Bunny did not even attend his own dad's funeral. Bunny accuses him of being stuck in the past and a loser, saddled with gambling debts and a drinking problem. Aditi stops them from fighting. Bunny & Avi eventually make up. Avi had seen each of Bunny's episodes. Bunny offers Rs 25 Lakhs to Avi to help renovate his bar.

Throughout the wedding celebrations, Naina's feelings for Bunny grow once again as they spend time together, with Bunny teasing her about a potential love interest whose texts he sees on her phone. Bunny too finds himself attracted to her.

The two spend the day touring Udaipur, discussing what they want from their lives. While Bunny describes wanting to travel the world, experiencing all he can, Naina espouses the virtues of settling down, having a large family, and remaining close to one's friends and home. Bunny later sees Aditi approach Avi to speak with him before being pulled away by Taran, who she starts fighting with.

Concerned that Taran is irrationally jealous of Adi speaking to Avi, Bunny asks her why she is marrying him. She reassures him that she approached Avi wanting to tell him off and slap him for splurging on booze and poker while Taran paid off his debts, and that Taran was actually holding her back to preserve her friendship with Avi. She says she has gotten over Avi and is much happier with Taran.

Bunny realizes that he feels the same way about Naina, but when going to express this to her, he sees her having a drink with another man and feels jealous, telling the man to leave and claiming to be her boyfriend. This causes the two to argue, and Naina tells him she can't keep spending time with him because she will fall in love with him again, and again he won't feel the same way. Bunny kisses her, and they confess they love each other, but neither is willing to give up their career and lifestyle to follow the other. Naina decides that it's best they forget each other, and they share a tearful goodbye.

Following Aditi's wedding, Bunny heads to the airport in tears to leave for Paris. At the airport, he recalls being there eight years prior and realizes the importance of what he is leaving behind. He goes back to his father's home, where he lets go of his previous resentment toward his stepmother and expresses his regret to her over not having seen his father before he died. His stepmother reassures him that his father wanted him to pursue whatever made him happy.

On New Year's Eve, Naina, alone at home, receives a surprise visit from Bunny. He explains that he has turned down his dream job in Paris to be with her and proposes marriage. She fears that he might regret his decision, but Bunny counters that he is happy with her and wants to continue travelling - but with her, arguing that they can make a life together. Naina concedes, and they have a call with Aditi and Avi. They all wish each other a Happy New Year and the film ends with Bunny and Naina embracing.