Kartar Singh (Anil Kapoor) is a Sikh settled in London. He has two brothers and a sister. One brother (Sanjay Kapoor) and his wife are killed in a road accident but the couple’s tiny twins have a miraculous escape. The two tiny tots become Kartar Singh’s responsibility but because he is unmarried, he gives one baby, Charan, to his other brother, Baldev Singh (Pavan Raj Malhotra), to raise, and the other baby, Karan, to his sister, Jeeto (Ratna Pathak Shah), to bring up. Charan grows up in Chandigarh in India as Baldev Singh runs a hotel, Purani Haveli, there. Baldev lives in Chandigarh with his wife (Geeta Agrawal Sharma) and daughter (Bhoomika Sharma). On the other hand, Karan is raised in London because Jeeto lives there with her husband (Lalit Parimoo) and daughter (Nikkita Chadha). Since Karan and Charan are identical twins, they grow up looking very similar. While Karan (Arjun Kapoor), rose in London, is flamboyant and outgoing, Charan (Arjun Kapoor) is shy and timid.

Karan has a girlfriend, Sweety (Ileana D'Cruz) from past 2 years. Unfortunately one day, they both are in the same mall talking on call as Sweety laughs and at the same time Sweety passes from the escalator where Karan's aunt/mom, Jeeto falls and misunderstands that she was laughing at her. They have a big quarrel with each other including Jeeto accuses her as a 'bad character girl' and dislikes her from now.

Meanwhile, in Punjab, Charan also has a girlfriend, Nafisa (Neha Sharma) who is a Muslim and studying law. So, trouble starts as Baldev decides to marry Charan with a respectful girl. Jeeto suggests her husband's friend Akalpreet Sandhu (Rahul Dev) who is also willing to marry their daughter Binkle (Athiya Shetty) with a good man. Jeeto decides to send Karan to Punjab so that he can manage Baldev's restaurant in his absence. So, Baldev takes Charan to London where Kartar welcomes them. Kartar first takes them to his 'Mini Punjab' residence and then to Jeeto's. While in Punjab, Sweety comes with Karan too as her father also lives there. In London, Charan consults with his uncle Kartar that he doesn't want to marry Binkle as he is in love with Nafisa. Stupid Kartar decides to help him with his creative ideas. He suggests him to act as a drug addict in front of Sandhus so that they will refuse themselves. Next day, Charan does the same but as he sees Binkle, he falls in love with her. Binkle takes Charan on a house visit while Kartar drops silly habits of Charan's drug addiction in Manpreet (Karan Kundra), Binkle's brother.

Charan tries to tell Kartar about his sudden feelings but just falls off the window due to signal problems. Due to this incident, Manpreet exposes and confirms Charan's drug addiction on which Baldev opposes and misbehaves. Jeeto and her husband instead of defending Baldev, they persuade him to apologize to Mr Sandhu for his misbehaviour but Baldev refuses to do so as he thinks it is against his ego. They return back home and blames Baldev for their disrespect in front of the rich Mr Sandhu and also offends him of his poor past. Baldev tolerates at his limit and decides to return to Punjab. He challenges Jeeto that he will marrynCharan at exact 25th of December with a girl much better than Binkle. They end their relationship. Meanwhile, Charan asks Karan to bring Nafisa at the airport so that he could talk about his feelings for her with his adoptive father. When they land in Punjab, Karan does what Charan asked and confronts them with Nafisa, but coward Charan doesn't dare to speak and Baldev misunderstands that Nafisa is Karan's girlfriend. This creates problems for Karan. Baldev overhears Sweety's father pleading for her daughter's marriage soon in gurudwara. So, Baldev takes Charan's proposal for Sweety who misunderstands her bond getting tied with Karan but later realizes it's tied with Charan. She gets upset and persuades Karan to do something about this. While back at London, Jeeto takes the proposal of her own Karan to Sandhu on which he agrees. They fix their marriage on 25th December too.

Kartar is split into Jeeto and Baldev's marriage events at the same date. To solve this problem, he suggests Baldev have a destination marriage in London, where he was insulted. Baldev agrees and everyone flies to London. Kartar accommodates Sweety and her father in a five-star hotel, and Charan and Baldev in front of Jeeto's residence, yet he wants to be alone. Wedding preparations continue with Sweety, Karan and Charan's plans to get rid of their problems. Charan decides to tell Binkle that Charan is marrying her without his consent. So, both families along with their in-laws gather in a mall for shopping. Charan takes advantage of this and reveals Karan and Sweety's relationship on which she is heartbroken, saying that maybe she lacks something as she is rejected by every man. Charan feels sorry for her and falls for her more because of her innocence towards him. Charan refuses to fight for his rights on which Karan invites Nafisa to London, increasing Charan's problems. Karan, Charan, Sweety and Nafisa decide to run with their love. But their plan fails when in the next morning Manpreet falls for Nafisa and Sandhu insist her to live at his residence. Nafisa and Manpreet fall for each other. Nafisa starts ignoring Charan. Charan wants to reveal his feelings for Binkle but at the moment, Nafisa appears and confess her love for Manpreet and leaves. Charan and Karan's marriages are planned at the same gurudwara as the date. Beforehand, Charan and Sweety's engagement is held which Jeeto attends alone from her side. Later, Karan and Binkle's engagement is held which Baldev's family attends alone.

Before Binkle's engagement, Charan confesses all the mishaps and misunderstandings happened and he is not drug addict too. He also reveals his feelings to her at last. After Binkle's engagement, Karan, Sweety, Charan, Binkle, Manpreet, Nafisa and Kartar gather at a place where Kartar refuses to help them and they would have to marry the ones chosen by their parents instead of eloping. So, 25th December arrives when Karan and Charan exchange their sherwanis, disguising as each other. At the gurudwara, Sweety reveals her love for Karan in front of everyone on which everyone including the twins because of their exchanged identities. Not to cause more trouble and confusion, they both take Kartar in confidential meeting revealing their exchanged identities where Kartar orders them to wear their original identities and never ever discuss this mishap with their wives. So, their families no more oppose their choices and Karan weds Sweety while Charan weds Binkle and they live happily ever after.