The story begins at IIM Ahmedabad, where the protagonist Krish Malhotra (Arjun Kapoor) is pursuing his MBA. Krish comes from a family very proud of their Punjabi heritage. One day in the mess hall, he meets Ananya Swaminathan (Alia Bhatt), who comes from a conservative Tamil Brahmin family. Krish and Ananya become friends and start studying together. During this time, Krish feels attracted to Ananya, but fears that she does not feel the same way because she has rejected several boys from IIT colleges, where Krish is also from. To avoid potential heartbreak, he abruptly stops studying with her without giving any reason. When Ananya demands to know what is wrong with him, he accidentally blurts out all his feelings for her. Ananya kisses him, indicating that she feels the same way, and the two begin dating and living together for their two years on the IIM campus. Krish tells Ananya that his real passion is writing, and that his dream is to make enough money from a steady job so that he can pursue a career in writing.
When their graduation comes, Krish and Ananya decide to get married. They introduce their parents to each other at the convocation ceremony. To their dismay, Krish?s loud Punjabi mother Kavita (Amrita Singh) does not get along with Ananya?s reserved Tamilian parents Radha (Revathi) and Shiv (Shiv Kumar Subramaniam). After the convocation, Ananya begins her banking job in her hometown Chennai and Krish goes back to his hometown Delhi and contemplates where to do his job. Kavita and her brash family urge him to stay in Delhi and try to discourage him from his interest in writing. They also criticize his relationship with Ananya, and tell him to get an arranged marriage with a Punjabi girl. It is during this time that the audience first witnesses the tension between Krish and his alcholic father Vikram (Ronit Roy).
Krish decides to leave his dysfunctional family in Delhi, and starts a banking job in Chennai. During this time, he tries very hard to win over Ananya?s family. He tutors her younger brother Manju, gets Radha an opportunity to sing at an event for his workplace, and helps Shiv create his first PowerPoint Presentation. After all his effort, Ananya?s family agrees to her relationship with Krish, and gives them the approval to get married. Krish and Ananya then travel to Delhi to win over Krish?s family. Initially, Kavita and her family are hostile towards Ananya because they still want Krish to marry a Punjabi girl. However, they come to like her after she saves Krish?s cousin?s wedding from being cancelled due to a dispute over dowry.
After Kavita approves of the marriage (Krish does not care about his father?s opinion), Krish and Ananya decide to take a vacation with their families before the wedding. The vacation does not go as smoothly as planned when Kavita makes continuous snide remarks about Tamilian culture and complains how she is not treated with gifts the way a Punjabi groom?s mother is traditionally treated. Shiv and Radha decide they?ve had enough and call off the engagement. When Ananya pacifies them and convinces them to give Kavita a second chance, they walk back in only to overhear Krish falsely assuring his mother that she can treat Ananya however she wants after they are married. Ananya does not want to start her marriage on lies, and calls off their engagement. They return to their respective hometowns.
Both Krish and Ananya find it hard to live without each other, and Krish also has a hard time finding a publisher for his manuscript. Sometime later, he gets a call from Ananya. She says that Vikram came down to Chennai to speak to her parents, apologizing for his wife?s shallow behavior. This allows for Krish and Ananya to finally have their happy ending. It is revealed that after they got married, they became parents to twin boys and Krish published his book 2 States based on his and Ananya?s story.