Supercop Bajirao Singham (Ajay Devgn) is posted to Mumbai for duty, where he meets the love of his life Avni (Kareena Kapoor) He also comes across his former school teacher Guruji (Anupam Kher) who is crusading against corruption and malpractices in politics and administration. Guruji has started his own political party whereby he gathers young professionals to lead his cause and bring a change. However, at the same time, Singham faces a tragedy when one of his closest constables suddenly goes missing and is found dead after few days in an ambulance carrying load of cash. This sets Singham's critics and the especially the media to question the integrity of his team.

On the other hand, he is also faced with two formidable and dangerous enemies Prakash Rao (Zakir Hussain) a corrupt politician and his aid, a rotten criminal and a rapist, who is masquerading in the form of a spiritual guru Swamiji (Amole Gupte). Unfortunately, the duo is in alliance with Guruji, who withdraw their support when they fail to convince him to give up his social cause.

This leads to Guruji not only separate him from their political alliance, but now also faces a threat to his work and his life. Tragically Guruji is killed in a deadly attack by the duo. Now Singham is restless and furious and will do anything to track down and kill these scums. This sets a bloody war of the good and the evil in Mumbai, where Bajirao Singham with the support of his police department fights against the corrupt and the powerful.