Two young progressive Indians, Nikhil "Nick" Arora (Saif Ali Khan) and Ambar Malhotra or "Amby" (Preity Zinta), have left India to live their lives in Melbourne, Australia. Nick was sent to Australia to become an architect. After graduating, he got a commission to design a restaurant, where he works as the head chef and the restaurant has been named "Nick of Time". His job allows him to have a laid-back lifestyle and get up late in the morning, both aspects that he values very much. In Bangalore, Ambar was shown twelve men for marriage and she rejected each one. Her parents suspected that she did not want to get married, however, she denied it. She went to Australia for a one-year foreign exchange program and decided to stay and become a surgeon. After hearing this, her parents cut off all ties with her. To pay for her education, she works as an R.J. at a local radio station, "Salaam Namaste".
When Nick is supposed to do an interview for Salaam Namaste, he oversleeps resulting in him getting insulted by Ambar on the air. His boss, Dheka, demands that he go to the radio station or he will 'kill' him. Nick oversleeps again and he is, once again, insulted by Ambar for being late. Nick is the caterer for one of Ambar's friend's wedding. His best friend Ranjan "Ron" Mathur (Arshad Warsi) falls in love with Ambar's best friend Cathy (Tania Zaetta) at the wedding. Nick also feels a connection with Ambar, although they have no idea who the other really is. Nick tells Ambar he is an architect. Ron and Cathy marry the next day and Nick and Ambar discover each other's true identities. Nick gives the interview on Salaam Namaste, where he states, publicly, that he loves Ambar. They both end up at Ron and Cathy's house, where the two just had a fight. Nick persuades Ambar to move in together, where they fall in love. Two months later, Ambar discovers she is pregnant. Nick takes her to get an abortion that she later tells him she did not have, resulting in a break up.
Over the next five months, they have several comical disagreements. Nick finds a restaurant to buy, but the loan is disapproved as he cannot afford the downpayment because he spent all his money on the house to live with Ambar. This results in another argument where the baby kicks for the first time and Nick realises he still loves Ambar. Ambar asks Nick to take a blood test because Ambar is thalassemia minor and if Nick is a thalassemia minor too the baby would have a problem. Nick goes to the hospital where he has his blood test and the doctor gives him a sonography, and informs him that Ambar is bearing twins. On the way home he thinks about what the doctor said to him and he realises that he has left Ambar alone through the whole pregnancy, when she needed him the most. He goes home and looks at the sonography and realises he still loves Ambar. He goes to buy an engagement ring and sees a pregnant Ambar trying on rings with her friend, Jignesh (Jugal Hansraj). Nick thinks that Ambar is marrying Jignesh and is devastated. He goes and gets drunk and takes a drunk girl home with him. When he wakes up, he is shocked, but the girl, Stella, is angry because he didn't do anything and was crying out Ambar's name all night. Nick is greatly relieved, but then Ambar sees her in the bedroom and is very upset and tells Nick she's moving out today. Nick discovers that when Ambar was trying on rings, it was for Jignesh's girlfriend, Tina. He searches for Ambar with the help of many devoted Salaam Namaste listeners. He finds her and apologises but, when he is about propose, Ambar's water breaks, and they rush to the hospital.
At the hospital, Ron is there with Cathy, who's giving birth as well, and the nurse turns out to be Stella. She tells Ambar that Nick didn't do anything the previous night and is in love with Ambar, who finally realises Nick's love for her. They then meet the obstetrician Dr. Vijay Kumar MDGGO (Abhishek Bachchan), who turns out to be a very comical and incompetent doctor, but manages to deliver the children. Ambar gives birth to twins and Nick proposes to her to which she joyously agrees.