A humanoid alien (Aamir Khan) lands on Earth naked on a research mission in Rajasthan, but is stranded when the remote control of his spaceship is stolen, though he manages to get the thief's cassette recorder, a National Panasonic RQ-565D. On the same day in Bruges, Jaggu (Anushka Sharma) meets a man named Sarfaraz (Sushant Singh Rajput) and falls in love with him. Jaggu's father (Parikshit Sahni) objects to their relationship because Sarfaraz is a Pakistani Muslim, while Jaggu is a Hindu. He consultsgodman Tapasvi Maharaj (Saurabh Shukla) who predicts that Sarfaraz will betray Jaggu. Determined to prove them wrong, Jaggu proposes to Sarfaraz. She is heart-broken at the wedding chapel when she receives a letter calling off the marriage due to their cultural differences.
Jaggu returns to India and becomes a TV reporter. She meets the alien and is intrigued at seeing him distribute leaflets about "missing" Gods. She saves him when he attempts to take money from a collection box, earning his trust.
He tells her that he was a research scientist from his planet. The people of his planet know nothing about dress, god and verbal communication. They transceive ideas by holding both of their hands with the person whom they are communicating. The longer they hold hands, greater information like language, skills, behaviour can be passed. After he landed on Earth, he learned to fit in among humans by wearing clothes and using money stolen from couples having sex in "dancing cars". After being accidentally hit by a truck, he was befriended by bandmaster Bhairon Singh (Sanjay Dutt), who took him along with his troop. Initially unable to communicate, he attempted to learn human language by grabbing peoples' hands and absorbing their memories through touch, but people chased him away, believing him to be a pervert. Bhairon took him to a brothel, where the alien held a prostitute's (Reema Debnath) hand for 6 hours and thus learned theBhojpuri language.
Bhairon had a conversation with the alien, and suggested that the thief may be in Delhi. The alien left for Delhi. Due to his strange behaviour, people assumed he was drunk and called him PK (pee-kay, Hindi for "drunk"); he adopted this name. People told him that only "God" could help him find his remote. PK sincerely practiced every Indian religionattempting to find "God", but to no avail. He later discovered that Tapasvi had his remote, that he claimed was a gift from God. Tapasvi refused to return the remote.
Jaggu promises PK that she will recover his remote so he can go back home.
PK conjectures that Tapasvi and other godmen must be dialling a "wrong number" to communicate with God, and are therefore advising the public to engage in meaningless rituals. Jaggu encourages the public to expose fraudulent godmen, by sending their videos to her news channel. This "wrong number" campaign turns into a popular mass-movement, to the dismay of Tapasvi. Meanwhile, Bhairon finds the thief and contacts PK, informing him they will come to Delhi, but both die in a terrorist attack.
Tapasvi decides to confront PK on-air. During the debate, PK says the "God that created us all" is the only one we should believe in, and that the other "duplicate Gods" are created by man. Tapasvi claims he has a direct connection to God and refers to his prediction of Sarfaraz's betrayal as proof. PK realizes that Sarfaraz did not write the letter. Jaggu contacts the Pakistan Embassy in Belgium where Sarfaraz worked part-time. The embassy tells her that Sarfaraz still loves her, and transfers the line to Sarfaraz. Jaggu and Sarfaraz reconnect, and Tapasvi is forced to return PK's remote.
Meanwhile, PK has fallen in love with Jaggu, but refrains from telling her because she loves Sarfaraz. Having filled multiple audio tapes with her voice alone, he takes two suitcases full of tapes and extra batteries when leaving for home. After his departure, Jaggu publishes a book about him.
One year later, PK returns to Earth on a new research mission on human nature along with several other aliens (including one played by Ranbir Kapoor).
