The Namesake describes the struggles between two first generation Bengali immigrants to the United States, Ashima Ganguli (Tabu) and Ashoke Ganguli (Irfan Khan), and their children, Gogol (Kal Penn) and Sonali (Sonia) (Sahira Nair). The featured locales are Kolkata, India, New York City, New York suburbs of Westchester and Oyster Bay.

The story begins as Ashoke and Ashima leave Kolkata and settle in New York. Through a series of errors and trials, their son's nickname, Gogol, becomes his official birth name, an event which will shape many aspects of his life. The film uses Gogol's struggles over his name as a jumping off point to explore large issues of integration, assimilation and cultural identity. The film chronicles Gogol's cross-cultural experiences and his exploration of his Indian heritage, as the story shifts between the United States and India. Gogol eventually meets and falls in love with two women, Maxine (Jacinda Barrett) and Moushumi (Zuleikha Robinson), while his parents struggle to understand his modern, American perspectives on dating, marriage and love.