Aadhavan (Suriya) is a professional assassin working with his father Ibrahim Rowther (Sayaji Shinde) and brother Tharani (Anand Babu). Doctor Abdul Kulkarni (Rahul Dev) hires Aadhavan to kill prominent Judge Subramaniam (Murali), since he is handling the inquiry and verdict on Abdul's child kidnapping, murder and organ trafficking cases in Kolkata. Aadhavan attempts to murder Subramaniam but fails at the first attempt. After Abdul insults him for his inability, Aadhavan is angry with himself and promises to kill Subramaniam within ten days. He threatens the Judge's comical servant Bannerjee (Vadivelu) to help him get into the house as Murugan, Bannerjee's brother in law, while he locks up the actual Murugan (Sathyan) in his ship.
Slowly Aadhavan begins to win over the members of Subramaniam's household - his mother (B. Saroja Devi), her beautiful granddaughter Thara (Nayantara) and his other relatives. Thara is attracted to Murugan's (Aadhavan) intelligence and simple-innocent nature. Aadhavan tries to assassinate the judge at home in the middle of the night and also plants a bomb in Subramaniam's van, but both attempts fail. Meanwhile, Subramaniam's entire family is on a trip to Darjeeling, and Thara asks Aadhavan to hide a guitar belonging to Ilaiyaman (Ramesh Khanna), her madcap musician cousin. Aadhavan uses this opportunity and plants a mobile bomb in the guitar and places it in one of the cars which explodes at the wrong time and he fails to kill Subramaniam yet again. Meanwhile, a security officer at Subramaniam's house keeps informing Abdul Kulkarni of Aadhavan's entry into the house and all his progresses and failed attempts.
Thara is now suspicious about Aadhavan but when she questions him in secret, he informs her that he is really Subramaniam's long lost runaway son Adhavan. Thara soon informs all the members of the household about Madhavan and they are overjoyed and Thara and Aadhavan fall in love. However, they hide it from Subramaniam alone, because of his hatred towards Madhavan. Aadhavan, however tells Bannerjee that he lied to Thara about Madhavan to distract her suspicion, and that he really is not that runaway son at all. However, on Thara's birthday, a flashback reveals that Aadhavan is indeed the runaway Madhavan.
Years ago, a ten-year-old Madhavan unknowingly carries a gift with a hidden bomb for his cousin Thara's birthday. His friend's mother plants the bomb in the toy to avenge Subramaniam for her husband's jail sentence. Though Thara survives, her mother Anu (Anu Hassan), opens the box and is killed along with her husband in the explosion. Subramaniam blames Madhavan for his sister Anu's death and for his friendship with a gangster's son and thrashes him. In anger and fear of going to a juvenile prison, Madhavan steals a gun from the cops and accidentally shoots his father and runs away from home. He saves a local goon, Ibrahim Rowther from death, and is in turn adopted as his son and rechristened as Aadhavan.
Coming back to the present, Abdul Kulkarni is fed up with the repeated failed attempts of Aadhavan. So he makes another plan and threatens Ibrahim and his gang to surrender to the police and make a confession about Aadhavan and his plans. When the Assistant Commissioner of police (Riyaz Khan), confronts Aadhavan and is about to have him hauled off, Aadhavan gets Subramaniam's laptop containing the verdict and inquiry reports, takes him and Thara as hostages and drives away. In the meanwhile, the police commissioner (FEFSI Vijayan) arrives and makes a confession that the police actually had caught him after his very first attempt to kill the Judge had failed. When questioned by the commissioner, Aadhavan said that he backed off and misfired on purpose at the last moment, after he found that he was going to kill his own father. The Police then ask him to go back to the house to protect his father over a twenty-four-hour period everyday. This information is relayed to the Judge who is tearfully grateful to his son. Meanwhile, Abdul Kulkarni attacks the vehicle in which the trio are travelling and a fight ensues where Aadhavan saves his father and Thara, and Kulkarny is killed.
As the credits roll, we see that Madhavan and Thara are now married and live in the household with the huge family, and yet again Bannerjee brings two assistants (K. S. Ravikumar and Udhayanidhi Stalin), to help him and asks approval from Madhavan and he gladly approves.Suriya as Aadhavan (Madhavan/Murugan)
Nayantara as Thara
Vadivelu as Banerjee/"Banner" Kuppan
Murali as Subramaniam
Saroja Devi as Subramaniam's mother
Rahul Dev as Abdul Kulkarni
Sayaji Shinde as Ibrahim Rowther
Anand Babu as Tharani
Ramesh Khanna as Ilaiyaman (Kuppusamy)
FEFSI Vijayan as Police Commissioner
Sathyan as Bannerjee's brother-in-law
Riyaz Khan as Deva
Manobala as Subramaniam's brother
Alex as Subramaniam's brother
Lakshmi Ramakrishnan as Subramaniam's sister-in-law
Anu Hasan as Thara's mother
K. S. Ravikumar in a special Appearance
Udhayanidhi Stalin in a special Appearance
The song "Eno Eno Panithuli" was shot at Iceland, making Aadhavan the first South Indian film to be shot there. Shooting also took place at the Chettinad Palace.
The soundtrack features 6 tracks composed by Harris Jayaraj; the lyrics were written by Vaali, Pa. Vijay, Na. Muthukumar. The soundtrack was released on 19 August by S. Shankar. The album received positive reviews from critics, with praise being dedicated to the songs "Hasili Fisile" and "Vaarayo Vaarayo". Malathy Sundaram from Behindwoods said "There is a lot of technical finesse to this album. What surprises us here is the banality of the lyrics! One would have expected better lyrics from all these songwriters!Harris Jayaraj has consciously used various instruments to add appeal to this album." Pavithra Srinivasan from Rediff said "Harris Jeyaraj is one of those composers who is not capable of turning out bad stuff even on a bad day, this album stands out from a mile away." Due to the album's critical and commercial success, Harris Jayaraj received the Vijay Award for Best Music Director and was nominated for the Filmfare Award for Best Music Director.
The satellite rights of the film were sold to Kalaignar.
Behindwoods gave a 2.5 out of 5 and gave a verdict "Carefree commercial – Conditions apply". Sify.com gave a positive review stating "Ranging through a wide field of comedy laced with action, Aadhavan is good fun while it lasts. It’s a roller-coaster ride of pure unadulterated masala".
Rediff rated the movie with 2.5 out of 5 stars and ended the review with "Aadhavan is uncomplicated, clean, fun, and doesn't expect you to take it seriously." Nowrunning.com also rated it as 2.5 on 5 and Aravindan D I specially said "Aadhavan could have been good entertainment, but is marred by inconsistent script." while Indiaglitz gave the verdict "above average" and stated "Aadhavan is a movie that would bring joy to mass action lovers and front-benchers.". Malathi Rangarajan from The Hindu wrote "Post-interval, you have to wait quite a while for some concrete action from Aadhavan, the Infallible!"
The movie collected ₹ 73 crore worldwide in its Lifetime Collection. This movie also had a high collection in Malaysia as well as UK. Overseas, the film grossed about $1,541,485, approximately. The film was a hit at the box office. The film was dubbed into Telugu as Ghatikudu. It is also dubbed into Hindi as Dildaar-The Arya. The film ran over 215 days in theatres.
The movie was remade in Bengali as Shikari starring Bangladeshi superstar Shakib Khan. Shikari is a 2016 Bangladesh-India joint venture action thriller drama film directed by Joydeep Mukherjee and Zakir Hossain Simanto.