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 aka Bunny (Ranbir Kapoor) is a carefree boy whose dream is to roam around the world, he doesn't believe in the marital bond. He lives with his father (Farukh Sheikh) and stepmother (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) were his best friends. Aditi loves Avi but had 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.

Those three friends planned to visit Manali. Naina (Deepika Padukone) was 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 (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.

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.

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. 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. Naina never reveals her love to Bunny as she knows that Bunny desires nothing by freedom in his life, so she decides to bury her feelings.

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.

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. 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 calls Avi a drunkard and a loser. 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.

Bunny & Naina spend a lot of time together & slowly Naina falls in love with Bunny all over again. Lara is also at the wedding and turns out to be Taran's London based cousin. Bunny helps Naina to win the wedding Sangeet dance contest between the bride's and the groom's sides. But again & again Bunny professes his love for his carefree lifestyle & his travels. Naina understands & again decides to step aside.

But this time, Bunny gets the hint. He realizes that a life without love is not worth a lot. He professes his love to Naina & manages to convince her to marry him. Naina is skeptical till the end as she does not believe that the bonds of marriage will tie Bunny down. Eventually she relents & the 2 get married.