Sathyam begins with Sathyam (Vishal), an assistant police commissioner rescuing a hooligan from encounter thirsty cops, only to arrest him later. He reminds his fellow cops that a cop's duty is to kill crime not criminals. Sathyam meets his first challenge in tracking a mysterious killer of three ministers. In the process, he finds the culprit Manickvel (Upendra), only to receive a rude shock to know his identity.
For, the murderer is none other than a former police officer, who inspired Sathyam to take the cop job. Revealing the reason behind his change of mind, the ex-cop says that he is on a killing spree as he failed to set right things in khakhi uniform.
Sathyam, who throws a challenge at his mentor that he would use the power of law to put the wrongdoers behind the bars, vows to throw light on the illegal activities of the Home minister (Kota Srinivasa Rao), who aims at the Chief Minister post.
In the meantime, the protagonist also has a romantic episode with Deivanayaki (Nayantara), a TV journalist. This begins with Deivanayaki suing the locality's children through their parents. The children swear vengeance through a 'gangleader' who happens to be none other than Sathyam himself. The 'gang' succeeds by making their rival a laughing stock with multiple pranks. Nevertheless the female does recognize Sathyam's tenderness at heart and falls for him. Sathyam too falls in love thereafter.
During his attempts to establish truth, Sathyam faces various troubles. The Minister's proxies give him various troubles by killing children by offering them ice creams laced with drugs to eat and killing his mother. When Satyam arrests Acharya, the Minister's proxy, and takes him to court, the Minister's henchmen attack him while driving and Satyam is stabbed. Thillanayagam, the other proxy, shoots Acharya and blames Sathyam. Sathyam performs his mother's funeral rites and is suspended from the force and jailed. Manickvel, to be released the next day, feels for Sathyam and laments his loss in the jail. Thillanayagam runs for MLA with the Minister's support so that he cannot be harmed by Sathyam. He gloats to Sathyam at the jail about his newfound power and challenges Sathyam's honor and dignity. At a public rally for Thillanayagam's candidature, the Minister openly challenges and insults Sathyam, who is released from jail by a sympathetic officer and coming to disrupt the public rally. Manickvel stands in the corner aiming to kill Thillanayagam and the Minister. Sathyam arrives and exposes the Minister and his proxy by shooting them and forcing them to confess the truth about the Minister's intentions and the death of the proxy. Thillanayagam reveals everything about himself, Acharya, and the Minister. While lamenting the situation he is in and calling for reform, Sathyam is shot by the Minister's henchman and questions the honesty and trust his people and fellow officers have in him. Manickvel arrives on the scene and salutes Sathyam, with other officers following suit. A newscast is shown with the Minister and Thillanayagam being arrested and Sathyam is reinstated. Sathyam is promoted to Deputy Commissioner by the Chief Minister and marries Deivanayaki, and the credits roll.Vishal as Sathyam I.P.S
Upendra as Manickvel (Prathap Rudra in Telugu version)
Nayantara as Divya
Sudha Chandran as Sathyam's mother
Premji Amaren as Bora
Livingston as a politician
Kota Srinivasa Rao as the Home Minister (Minister Kondal Rao in Telugu version)
Senthil as Paneerselvam
Krishna Kumar as Mohammed
Brahmanandam as the transport office broker
Ravi Kale as Delhi
Ali as Divya's assistant
Tanikella Bharani as Doctor
Vishal Krishna has been training hard for this role, pumping iron. He has also sported a neat short-cropped hairstyle to look like a serious law-abiding police official. This is the first time he is undergoing image makeover for a film in order not to be stereotyped as an action hero. Vishal's brother, Vikram Krishna Reddy, the film's producer, has revealed that the film is about police encounters, a very prominent issue regarding the laws of India. Hence, the protagonist's role runs parallel to that of Surya Sivakumar's in Kaaka Kaaka.
Trisha Krishnan was originally selected to do the lead role in Sathyam. Later she was removed and the selection was then between Nayantara and Shriya Saran. At last, Nayantara was selected to play the female lead. The film marked the debut of Kannada actor Upendra in Tamil cinema.
The film has five songs composed by Harris Jayaraj, "Sathyam" was his 25th film as music director. Lyrics are penned by Pa. Vijay, Kabilan & Yugabharathi. The soundtrack received generally positive reviews from critics. IndiaGlitz described the album as "catchy" and stated that "Harris has given his heart out to package it with the right mix of songs. With good vocals and perfect rhythms, Sathyam songs would be remembered by music-lovers for a long time to come. Sathyam is one more jewel in Harris's crown". Behindwoods mentioned that "Harris Jayaraj has not disappointed us here. But at the same time there’s nothing that sweeps us off our feet too."
Lyrics are written by Chandrabose, Sirivennela Sitaramasastri, Sahiti G.