Prem (Salman Khan) is married to the loving yet traditional Pooja (Karishma Kapoor), and together they have two children. One day, a model named Rupali (Sushmita Sen) arrives at Prem’s office to give interview for the role of a model. Prem and Rupali slowly start liking each other and ultimately both fall in love with each other. Rupali is much more preferable to Prem due to her modern lifestyle and fashionable choices, as compared to Pooja. On Karva Chauth, a religious ceremony observed by married couples, Pooja discovers Prem at Rupali’s house and asks him to choose between his mistress and his family. Prem chooses Rupali and moves in with her, leaving his children and mother behind with Pooja.
Pooja, meanwhile, with the help of Prem’s friend Lakhan (Anil Kapoor), has a make-over, becoming a modern woman and taking on modeling assignments. Pooja sends her mother-in-law and children to live with her husband and Rupali. They intentionally trouble Rupali and convince Prem that Rupali keeps them hungry and wants to poison and kill them. Ultimately the relationship between Prem and Rupali breaks down.
In the end, Prem realises that Rupali only came to him since he gave her material things, while his wife stuck with him through thick and thin. Rupali realises her mistake and gets back together with her ex-boyfriend, Deepak (Saif Ali Khan). In a twist, Lakhan befriends Rupali, affectionately calling her his sister. While hugging her, his wife Lovely (Tabu) walks upon them and misunderstands the situation. She leaves the house crying, but Lakhan chases after and they make up;with Lakhan saying she is his “Biwi no. 1.”