Thiruvilayadal Aarambam movie is about Thiru (Dhanush) and his fight to prove himself to the world. He spends his time in the lark-filled company of his buddies (Sukumar, Karunas). But the rest of the world thinks them to be useless dross. Thiru’s parents (Mouli and Saranya) too have little hope on their ward. In one of the family fights, Thiru is ordered out by his dad.
The youngster is out on his own. He then comes across Priya (Shreya) who is the sister of businessman Guru (Prakash Raj). Thiru tells Guru that he loves Priya. But Guru, being a rich man wants him out of the picture. Thiru also wants to get rich. Guru fixes deal with the dreamy young man. But he has to get the money as well as the girl.
Whether Thiru is able to win the acceptance of Guru & take his sister's hand with his permission forms the rest of the story.