Aditya (Vivek Oberoi) is a bright young law student. He meets Suhani Sharma (Rani Mukerji) on a wedding function. She is a medical student who scorns love and romance as trivial diversions.
He is immediately attracted to her, but she spurns him. Aditya is relentless and she is driven to admit that yes, she is attracted to him too. All seems set for a big wedding, but their two families meet and then fight. The couple after a failed attempt to avoid each other decide to break all rules, move into a dilapidated apartment and start an at-first-blissful married life.
Most Bollywood movies would end here. Saathiya, however, follows the couple into the difficulties of marriage. Aditya is busy and pre-occupied; Suhani feels neglected. They fight frequently. Then Suhani disappears.
Has she left Aditya because the marriage has become so painful? Aditya searches for her desperately and finally finds her in the hospital. Suhani has been badly hurt in an accident. She is in a coma and may not live. Sitting by her bedside and thinking over their lives together, Aditya realizes that he loves his wife deeply and that he wants to make a go of their marriage. He pleads to his unconscious wife to wake up and return to him -- which she does. All ends happily.