Michael Rayappan is a crime boss from Chennai who works for the welfare of people in his slum. He has a romantic relationship with Angel Aasirvatham, a physiotherapist who comically refuses to marry any groom at the last minute due to their love and every time Angel refuses an arranged marriage, her father gets beaten up by the church reverend. He has a running feud with a rival don named Daniel. One night, Daniel attacks Michael and his close friend Kathir, who is the coach of the Tamil Nadu women's football team. Kathir suffers spinal injuries during the attack, due to which he is paralysed for a year. To allow the women's football team to take part in the upcoming National Championship in Delhi, Kathir requests to the Tamil Nadu Football Federation to replace him with his former teammate named "Bigil", who is none other than Michael. The story then shifts to Michael's past as a football player.
Seven years earlier, Michael was an aspiring footballer and contributed to victories for the Tamil Nadu football team along with Kathir. His father was Rayappan, a don who had a feud with a rival don named Alex, who was Daniel's father. Rayappan encouraged his son's passion for football as he did not want him to end up as a criminal like him. When Michael was unable to make it to the Indian football team due to Rayappan's criminal record, Rayappan personally took up the matter with the All India Football Federation president J. K. Sharma and forcefully ensured Sharma to include Michael and Kathir in the Indian team probable list. But despite Rayappan's efforts, Michael's football career was cut short as he witnessed his father Rayappan getting stabbed to death by Alex and Daniel, just when he was about to leave for Delhi to attend the selection trial for the Indian football team. Michael killed Alex in front of Daniel, taking revenge for his father Rayappan's death, and instead stayed back in Chennai to become the new leader of his father Rayappan's gang.
In the present day, Michael confronts Daniel and attempts to kill him for the earlier attack, but fortunately the police intervene to arrest Daniel and send him to prison. Michael later accepts Kathir's request to coach the women's football team and leaves for Delhi with the team, with Angel also accompanying them as team physiotherapist. However, due to his criminal background, the girls refuse to cooperate with him, even blaming him for the team's opening loss to Manipur in the National Championship and requesting the Federation to have him removed. One of the players, Vembu has a grudge on Michael. Dejected, Michael gives his resignation to Sharma, but he soon discovers that Sharma is targeting him in revenge for the humiliation that he had faced at the hands of Rayappan to allow him into the Indian football team. Sharma sends armed assailants to attack Michael; however, Michael subdues the assailants and withdraws his resignation. He convinces the girls to support him and starts training them hard with the sole focus of winning the Championship. He even manages to bring back two former key players to boost the team's strength: Gayathri, a Brahmin girl who quit playing football after she was married to a conservative family; and Anitha, who is in depression and has refused to even leave her room ever since a man threw acid on her face when she spurned his advances. Despite Sharma trying to rig the team's next match against Haryana so that they will be eliminated and sent home, they manage to beat Haryana and win all their remaining matches, eventually qualifying for the Final at Chennai, where they are able to play against Manipur again. At their celebration party, Angel and Michael get engaged.
On the eve of the final, Vembu, is kidnapped and forcefully injected with cocaine by Daniel, who is bailed out from jail and hired by Sharma in order to sabotage the team's chances of winning the Championship. Though she recovers, she is unable to play in the final as she would fail the dope test. The team's captain, Thendral, is also kidnapped by Daniel, who attempts to forcefully inject cocaine on her as well; Michael also gets kidnapped by Daniel and gets injected with cocaine. Michael manages to beat Daniel's men and chases Daniel to his house and proceeds to kill him once and for all, but once he sees Daniel's young son, he changes his mind and spares Daniel, as he realises he does not want the young boy's future to end up like his by killing his father. The next day, Tamil Nadu plays the final against Manipur without Vembu. The match turns out to be a thriller with Tamil Nadu winning the Championship through a penalty shootout. Michael and the team dedicate their success to Kathir, who is watching the match from the dugout in a wheelchair. Vembu finally ends her grudge on Michael by telling him, "Sorry, Coach."
During the credits, Michael gets Sharma exposed for drug possession, leading to Sharma's arrest and subsequent execution in Malaysia, where he is on a holiday. A few months later, Michael, no longer a rowdy, takes up football coaching for children, with one of his students being Daniel's son, both of whom have now made peace with Michael and this film ends with Michael takes Daniel son and ask him who is your favourite football player Messi or C Ronaldo then he replies happily bigil is my favourite player then he takes him by saying vaa nanba means come my dear buddy.
