The film opens with Munna Bhai (Sanjay Dutt), a dreaded Mumbai-streeted goon, on the chase to Pillai (Ashish Vidyarthi). Munna Bhai catches him, and Pillai tries to escape into Komal's (Aishwarya Rai) dancing class. Komal stops Munna from beating him up and makes him say sorry to Pillai. Munna straight-away falls in love with her without realizing that he is in love. Noticing that Munna Bhai seems to be ill, his sidekick takes him to Dr. Rastogi (Amitabh Bachchan), whose diagnosis is that Munna Bhai is suffering from the "love virus" which can only be cured with love. He advises Munna Bhai to try to woo the girl with whom he is smitten. What Dr. Rastogi and Munna Bhai do not realize is that this girl is none other than the doctor's younger sister. Rastogi takes Komal abroad to get her married, unaware she is in love with Raja (Ajay Devgan). Raja, in disguise fools Rastogi, and follows them abroad. Munna Bhai is then on gun-point by Pillai, and Raja saves him. Unaware of knowing they both love the same girl, Rastogi makes a torn between them, which ends up getting Raja beat up. Munna Bhai gets his gun out, but before Rastogi realizes what he has done, Komal jumps in to save Raja and is shot. Munna Bhai realizing his mistake, surrenders, and gives up the crime world, while Dr. Rastogi also realizes his mistake and lets Komal marry Raja.
Amitabh Bachchan as Dr. Rastogi
Sanjay Dutt as Munna Bhai
Ajay Devgan as Raja
Aishwarya Rai as Komal
Satish Kaushik as Pappu Pager
Anu Kapoor as Munnu Mobile
Paresh Rawal as Commissioner
