Kanji Lalji Mehta (Paresh Rawal) a middle-class Gujarati atheist, owns a shop of Hindu idols and antiques in Mumbai. He mocks religious activities around him until one day, a low-intensity earthquake hits the city, with Kanji's shop being the only one destroyed; his family and friends blame this on his atheism.
At the insurance office, Kanji learns that the disaster claim does not cover any damage caused by natural calamities classified under "Act of God". Running out of options, he decides to sue God but fails to find a lawyer for such a lawsuit. Hanif Qureshi (Om Puri) a working class Muslim lawyer, helps him file the case after Kanji decides to fight on his own. Legal notices are sent to the insurance company as well as to religious people like Siddheshwar Maharaj, Gopi Maiyya, and their group's founder, Leeladhar Swamy, forcing them to court as representatives of God.
As the court case commences and gains attraction for its bizarre quality, Kanji finds himself facing armed fundamentalists and harassment, with his mortgage provider occupying the house, and his family leaving him. He is then rescued by Krishna Vasudev Yadav (Akshay Kumar) who claims to be a real estate agent originally from Gokul, Uttar Pradesh, yet is also responsible for supernatural acts outside of the human realm.
The lawsuit causes a public outcry. On Krishna's advice, Kanji goes to the media and gets wide coverage. Sympathisers join him in the lawsuit, causing the amount of claims to skyrocket and Catholic fathers and Muslim Maulvis to also be forced as defendants. When the court demands written proof that the earthquake was an 'Act of God,' Krishna steers Kanji toward holy books such as the Bhagavad Gita, The Holy Quran and Bible. Kanji reads them and finds a passage in each that says the world and all events are a creation of God and come from God's will alone. This strengthens his case and increases public support. However, Kanji suffers a stroke in court and is rushed to the hospital where he goes into a coma and is paralyzed. When he opens his eyes after a month, he finds Krishna, who reveals that he is god, and proves it by curing Kanji completely. He further reveals that He created the entire world, animals and humans but religion was created by humans, and he was the one who destroyed Kanji's shop because he sought to punish the godmen who showed his fear to the public, to earn money. He adds that he created the entire world and thus does not like to live in temples contrary to what the godmen claims and he is not interested in the offerings he gets from devotees. Instead, he created millions of humans who die of hunger and would be glad if those offerings were given to them instead. He figured out that an atheist like Kanji would end up exposing them if he destroys his Shop, and thus destroyed it by causing the disaster and started to help him with lawsuit by appearing as a human and befriending him and revealed himself in his true form so that Kanji realises that although he does exist, he does not live in temples, but in every creature he created.
Kanji learns that the lawsuit's verdict was in his favour, and religious organizations were ordered by the court to pay the compensation to all the plaintiffs. As a result of this, people have begun revering Kanji himself as a god. Leeladhar, Gopi Maiyya, and Siddheshwar have taken advantage of this by opening a temple dedicated to Kanji, and accumulating millions in donations. Krishna explains to Kanji that his job as God is to show people right and wrong – people do with it what they will. Kanji decides to fight back. He breaks his own statue, admonishing the crowd about trusting in God-men. He advises them to search for God in themselves and in others, not in statues; that God is everywhere, not just in temples, and faith should come from within. He tells them not to believe in fraudulent godmen, as their job is to turn religion into business.
After successfully completing the job he goes back to Krishna to thank him only to find him and his motorcycle disappeared Kanji’s family arrives and they get reunited together on their way home Kanji sees Krishna keychain on the ground. When he is about to keep it, he hears Krishna's voice, telling him to get rid of the keychain as fear of God and reliance on religious objects was what he'd fought against. Kanji smiles and throws it away, watching as it disappears into the sky with a flash.