Munnabhai (Sanjay Dutt) is a dreaded but good-hearted underworld don of Mumbai. The police are trying to implicate him on criminal charges, but so far they have not been successful because of lack of evidence against him. Once when Munnabha is beating up one off his foes, he sees Komal (Aishwarya Rai)...
Munnabha is smitten by her beauty so much so that he starts visualizing her wherever he goes or in whatever he does. Munnabhai or his men cannot understand this new phenomenon in Munnabhai' life. Because of this he stops taking part in his usual underworld activities like extortion or kidnapping. His men decide to take him to Dr. Rastogi (Amitabh Bachchan). The doctor realizes that its a 'love virus' and nothing else so he advice Munnabhai to woo the girl some how, not realizing that the girl Munnabhai has fallen for is nobody else but his own sister Komal.
Munnabhai starts wooing Komal. But she is in love with Raja (Ajay Devgan). A local riff-raff doing nothing much except working in a bowling alley as an instructor. The doctor is ignorant of their love affair. Munnabhai makes the doctor's life miserable because Komal does not respond to his advances as per advice given by the doctor. It's not long before the doctor realizes that his underworld patient has been in love with his own sister, so he decides to take her to Malaysia and get married off. This puts Raja in a dilemma.
He can't tell the doctor because of his social status and he can't even let Komal get married to someone in Malaysia. He also manages to go to Malaysia to go to Malaisia with the doctor and Komal. Not be left behind even Munnabhai follows them. Here all beans are split when the doctor gets to know about Raja and Komal's love affair. And then they get to know Munnabhai's intentions. Raja who once saved Munnabhai's life tells the doctor not to worry. 'He owes me a favour. I will handle him.'
Raja then talks to Munnabhai about Komal being his love. Munnabhai hits the roof with rage and he warms Raja to go away from Komal. Raja on the other hand tries to get rid of Munnabhai in Malaysia but nothing works. So the doctor, Komal and Raja decide to stay back in Malaysia forever and never to return to Mumbai as Munnabhai is helpless in Malaysia. Munnabhai plays a smart one on them and they are all deported back to Mumbai where Munnabhai is the uncrowned king.
What happens after they all land in Mumbai?
Will the doctor be able to save Komal from the don? Will Raja be able to convince the doctor and Munnabhai about his love.
This is a rip-roaring comedy directed by the don of comedy films DAVID DHAWAN.