Prem (Salman Khan) is a man who is married to Pooja (Karishma Kapoor) with two kids. He gets involved in a roaring affair with an aspiring model, Rupali (Sushmita Sen). He prefers her to his wife because Rupali is modern and wears fashionable clothes. On Karva Chauth, Pooja discovers him at Rupali's house and asks him to choose between his mistress and her. He moves in with Rupali.
Pooja, meanwhile, with the help of Prem's friend Lakhan (Anil Kapoor) has a make-over. She becomes a modern woman who does many modeling assignments. Pooja sends her mother-in-law and children to live with her husband and Rupali. They trouble Rupali and convince Prem that Rupali keeps them hungry and wants to poison and kill them.
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 makes Rupali his sister and is hugging her when his wife Lovely (Tabu) walks upon the scene and misunderstands them. She leaves the house crying and drives away in a car, which their son has tampered with and has disabled the brakes. Lakhan chases after and makes up with her. The show ends with Lakhan saying she is his "Biwi no. 1."