Dil Hai Tumhara is a film about two sister Nimmi (Mahima Chaudhary) & Shalu ( Preity Zinta ) who live with their strict mother Sarita (Rekha). Shalu is the daughter of Sarita's husband with whom he had been having an affair with. Hence most of the times, Shalu is neglected while Nimmi gets more affection from Sarita. One day a man named Dev Khanna (Arjun Rampal) arrives in the the lives of these girls. Nimmi believes Dev loves only her. Her mother is not aware of Nimmi's story & so she offers a marriage proposal to Dev's father (Alok Nath). Sarita sees Shalu giving love and attention to Dev & in anger reveals her true nature. Shalu decide to sacrifice her love by convincing that purposely she befriended Dev to steal him from Nimmi. Dev is confused & offers again to marry Shalu. To avoid any problem occuring during the marriage, Shalu goes to Dev's house & announces that she is illegitimate and praises Sarika for adopting her. Nimmi is happy that Sarita has accepted Shalu. She just feels that something is wrong with her sister. Shalu diverts Nimmi's thinking by giving her love to Samir (Jimmy Shergil), her best friend from childhood. Nimmi learns from Samir about the whole since & makes way for the relationship of Shalu & Dev.