It tells the story of a young man, Prem (Salman Khan), and a young woman, Nisha (Madhuri Dixit), who are both very fun loving, cheerful and mischievous. Prem has lost his parents at an early age. He lives with his elder brother Rajesh (Mohnish Bahl) and uncle Kailashnath (Alok Nath). Rajesh manages his business with great flair and his family is on the look-out for a suitable bride for him. Professor Siddharth Chaudhary (Anupam Kher) and Mrs. Chaudhary (Reema Lagoo) have two daughters, Pooja (Renuka Shahane) and Nisha. The Chaudhary couple and Kailashnath are old friends who meet again after several years. They arrange a marriage between Rajesh and Pooja. From their first meeting, Nisha and Prem start arguing and fighting with each other, although in a lighthearted manner. The fun and mischief continues throughout Pooja and Rajesh's wedding.
Prem gets along well with his kind and affectionate sister-in-law. In course of time, Pooja and Rajesh discover that they are expecting a child. Professor and Mrs. Chaudhary are unable to come to Kailashnath's house for the ceremony marking the impending arrival of the baby. So they send Nisha instead; and she stays there until Pooja's delivery. In the meanwhile, Nisha and Prem fall in love with each other. Pooja gives birth to a son. Professor and Mrs. Chaudhary come over to Kailashnath's house to celebrate the birth of their grandchild. When it is time for them to leave, everybody is sad, especially Prem. He and Nisha promise to each other that they will soon get together for ever.
Then, one day, Pooja gets invited to stay at her parents' house, and Prem takes her there. When they arrive, Pooja finds out that Prem and Nisha love each other. She promises to get them married and gives Nisha a necklace as a token. Then the phone rings and Pooja goes to answer it. She is happily hopping down the stairs when her foot accidentally slips. She dies from a head injury after falling off the stairs. Everybody is shattered by the tragedy.
Nisha takes good care of her dead sister's son. Hence, her parents and Kailashnath feel that Nisha will be a great mother to the baby. They decide to get Nisha married to Rajesh. Nisha overhears her parents talking about her marrying into Kailashnath's family. She mistakenly thinks that they are discussing her marriage to Prem. Later, at a pre-nuptial ceremony, she finds out that she is actually supposed to get married to Rajesh.
Prem and Nisha agree to sacrifice their love for Rajesh and the baby. Moments before the wedding is to begin, Nisha sends Prem the necklace that Pooja had given her, along with a letter. The letter and necklace fall into the hands of Rajesh. He realizes that Prem and Nisha love each other. He confronts both of them. In the end, Nisha and Prem marry each other with the consent of their families.