The film starts with Munna Bhai [Sanjay Dutt], a dreaded Mumbai-streeted goon, waiting for his enemy Pillai [Ashish Vidyarthi] to arrive, so Munna, and his man Pappu Pager [Satish Kaushik] can attack him. Munna had found Pillai while he was young, and he taught him how to murder, kill, attack and self-defence, now Pillai is using his own teached-skills on Munna, and that is why Munna wants to kill him. Pillais uncle, a kind-hearted man tells Munna to make his hatred into friendship, and while he is explaining that, Pillai jumps out ready to shoot Munna as his uncle jumps front and takes the bullet. He dies at that point, as Munna beats Pillai up. He chases him into Komals [Aishwarya Rai] dancing class, and then stops Munna from beating him up and explains to him the same that his uncle did. 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. Malhotra [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. Malhotra and Munna Bhai do not realize is that this girl is none other than the doctors younger sister. When Dr. Malhotra finds out, he straightly takes Komal to his friends house to get her married to his young son, unaware that Komal is in love with Raja [Ajay Devgan]. When Raja pranks Dr. Malhotra into thinking that Raja does not love his sister, he persuades him to take him along to get her married, as Raja will not let that happen. Munna Bhai then follows Dr. Malhotra and lands right onto his feet saying that he will die if he doesnt get Komal. That is when Munna Bhai gets a gun-victim and is saved by Raja, and Raja wishes that for saving his life, Munna Bhai should convince his girlfriends brother to get them married, and Munna Bhai accepts, unaware of knowing its Komal. When he finds out, they both create a torn between eachother and start a fight saying that who ever gets her first, gets the girl, and when Raja is first, Munna Bhai shows up and shoots him, and once again Komal takes the bullet. Komal nearly dies, as she sees Munna Bhai saying he gives up the Crime World, and surrenders. Komal gets back healthy, and marries Raja with Dr. Malhotras concept.