Director: Nikkhil Advani
Writer: Niranjan Iyengar
Jaya Bachchan as Jennifer Kapur
Shah Rukh Khan as Aman Mathur
Saif Ali Khan as Rohit Patel
Preity Zinta as Naina Catherine Kapur (later Patel)
Sushma Seth as Lajjo Kapur
Reema Lagoo as Aman’s mother
Lillete Dubey as Jaswinder “Jazz” Kapoor
Delnaaz Paul as Jaspreet “Sweetu” Kapoor
Shoma Anand as Kammo
Kamini Khanna as Vimmo
Ketki Dave as Sarlaben Patel
Sulbha Arya as Kantaben
Athit Naik as Shiv Kapur
Jhanak Shukla as Gia Kapur
Simone Singh as Camilla (special appearance)
Satish Shah as Karsanbhai Patel
Rajpal Yadav as Guru
Dara Singh as Pritam Chaddha
Sanjay Kapoor as Abhay (special appearance)
Kajol as a dancer in the song “Maahi Ve” (special appearance)
Rani Mukerji as a dancer in the song “Maahi Ve” (special appearance)
Sonali Bendre as Priya (special appearance)
Dheepesh Bhatt as Frankie
Anaita Shroff Adajania as Geeta Parekh
Anil Mehta as Naina’s father (uncredited)
Farah Khan and Karan Johar as customers in Jenny’s restaurant (uncredited)
Uday Chopra as a narrator who says “Day 6” (uncredited)
Naina Catherine Kapur is a pessimistic, uptight MBA student who lives in New York City with her widowed mother Jennifer Kapur, her disabled brother Shiv, her adopted sister Gia, and her paternal grandmother Lajjo. Jennifer runs an unsuccessful café with her neighbour, Jaswinder “Jazz” Kapoor. Lajjo is hostile to Jennifer and Gia as she believes that Gia’s adoption led her son (Jennifer’s husband and Naina’s father) to commit suicide.
Naina has two best friends: her classmate, Rohit Patel, and Jaspreet “Sweetu” Kapoor, Jazz’s sister. Her life is dull and overshadowed by her father’s loss until Aman Mathur and his mother move in next door with his uncle, Pritam Chaddha. Aman’s cheerfulness gradually wins over Naina’s family and he slowly starts to solve their problems. He suggests that they change the café to an Indian restaurant and its success alleviates their financial burdens. Aman encourages Naina to be happy and to live life to the fullest; she falls in love with him.
Rohit also falls in love with Naina and asks Aman’s help in expressing his feelings. Naina tells Rohit there is something she must say to him, leading him to think that she reciprocates his feelings. Naina reveals she is in love with Aman instead. Shaken, Rohit calls Aman to tell him what has happened. Naina goes to Aman’s house and is shocked to see a wedding photograph of Aman and his wife, Priya. Heartbroken, she leaves.
Aman’s mother confronts him about what has happened. He says he loves Naina, but has decided to hide it because he is dying from a heart condition. He is not actually married; Priya is his childhood friend and doctor. Aman vows to bring Naina and Rohit together before he dies. He believes that Rohit will be able to provide for her better than he can. He hatches a plan to transform Naina and Rohit’s bond, and gradually their friendship blossoms into love. Naina discovers his plan and chides Aman for trying to ruin her friendship with Rohit. Aman takes out Rohit’s diary and confesses his feelings for Naina, saying they are Rohit’s. Naina forgives Aman and Rohit.
Rohit proposes to Naina, and she accepts. Lajjo and Jennifer argue about Gia, who calls on Aman for help. Despite Jennifer’s objections, he reveals to Lajjo that her son had an affair and fathered Gia. When Gia’s biological mother refused to accept her, Jennifer adopted her. Unable to deal with the guilt, Jennifer’s husband committed suicide. Lajjo realises her mistake and reconciles with Jennifer and Gia.
During Naina and Rohit’s engagement, Aman has a heart attack. Only his mother knows he has been admitted to the hospital. Naina encounters Priya at a jewellery store, whom she recognises as Aman’s wife. She introduces herself and her husband, Abhay, who reveals the truth about Aman. Shocked, Naina realises that Aman has sacrificed his love for her and leaves the mall in an emotional frenzy. Priya calls up Aman and informs him about what happened. Aman leaves the hospital and meets a frustrated Rohit, who asks why he and not Aman should marry Naina. Aman urges Rohit to marry Naina as a sign of respect for his dying wish to see Naina happy. Aman meets Naina, and they embrace while he tries to persuade her that he does not love her. Rohit and Naina’s wedding, in which Aman attends, takes place soon afterward.
Sometime after the wedding, Aman is on his deathbed and says goodbye to everyone. He is left alone with Rohit after Naina leaves the room in tears. He makes Rohit promise that, although Naina is his in this lifetime, he will get her in the next. Twenty years later, Naina tells a grown-up Gia how Aman affected every aspect of their lives. They are joined by her daughter Priya and Rohit, who tells Naina that he loves her as they embrace.