Naan Mahaan Alla story begins with Jeeva (karthi) who is a typical Chennai youngster believing in taking life as it comes. He has his group of friends and his share of fun and is doted upon by his father Jayaprakash (jayaprakash) who is a call taxi driver. Meanwhile, Jeeva also comes across Priya (kajal) and eventually, they fall in love. The story takes a turn when Jayaprakash witnesses a kidnapping and goes out of his way to seek justice. However, he gets killed by the villains. Jeeva is shattered by it and decides to avenge the killers. What happens from there forms the rest of the story.