Vijay (Joseph Vijay) is a rich young business man, whose only one aim in life is to have fun, is the managing director of a big tea estate in Ooty and his company goes on a big loss because of his mismanagement. Vijay spends most of his time in partying and flirting with girls whenever he feels like. To manage the loss to his company, Vijay invites his father Rajasekar (who is in the United States) to come to India to sign some documents. As fate would have it, Vijay's father dies in a plane crash on his way to India. His maternal uncle (Manivannan) comes up with the idea of having another elderly person to act as Vijay's father for a while until the documents are signed. So they visit a senior home, where they meet Selvam (Sivaji Ganesan) and they request him to act as Vijay's father. He agrees to it and starts to act as Vijay's father.
Selvam observes the careless, take-it-easy life style of Vijay and is reminded of his old days when he used to be like Vijay (movie clips from an old Sivaji film Iruvar Ullam come to help). Selvam is very affectionate towards Vijay and he considers him as his son. Vijay finds out about Selvam's past life, that Selvam was married to Shantha (B. Sarojadevi) and they have been living separated for the past 30 years. He wants them to get united and he searches and finds the whereabouts of Santha. Meanwhile, Kavitha (Simran Bagga) joins Vijay's company and she talks to Vijay in his own style. Vijay is knocked out by Kavitha's beauty and he falls in love with her. Then, their love gets into trouble because of Kavitha's mother. Now, Vijay tries to unite Selvam and Santha. In return Selvam tries to unite Vijay and Kavitha. Will Selvam and Shantha meet and get married 'Once More'. Will Vijay and Kavitha get married 'At least Once' forms the rest of the story.
