In 2028, multinational conglomerate OmniCorp is at the center of military "robot soldier" technology, supplying the US Military with mechanical soldiers that are used overseas. OmniCorp wants to sell their products for use in civilian law enforcement in the United States but public opinion, embodied by the Dreyfus Act, prevents this. OmniCorp CEO Raymond Sellars (Michael Keaton) asks his marketing team, in conjunction with scientist Dr. Dennett Norton (Gary Oldman), to create a new law enforcement product by combining human and machine that he believes can be "sold" to the American public. They begin looking for a police officer who was permanently injured to act as the core of their prototype.
Policeman Alex Murphy (Joel Kinnaman) is critically injured by a carbomb planted on orders from a local crime boss Antoine Vallon. Norton picks Murphy for the RoboCop program, and with consent from Murphy's wife, Clara (Abbie Cornish), has him outfitted with the RoboCop body and software. Alex at first rejects his current condition, but is convinced by Norton to be strong for his wife and son. Rick Mattox (Jackie Earle Haley), OmniCorp's military tactician, is skeptical of Alex's abilities, saying he will never be as efficient as a fully mechanical robot. In order to make Alex perform better, Norton tampers with Alex's brain, making him believe that his tactical decisions are his own when he is actually executing programs.
While preparing for a public press conference to unveil RoboCop, Alex is emotionally overwhelmed and has a seizure while Norton is downloading the police database information into his brain. Pressed for time, Norton alters Alex's brain chemistry, lowering his dopamine levels until he no longer displays any emotions. Under control, Alex attends the press conference, where he ignores his waiting wife and son, and efficiently apprehends a criminal in the crowd. RoboCop is a public relations success, and drastically reduces the crime rate in Detroit. Public opinion on the Dreyfus Act begins to turn. Norton is told to prevent Alex from seeing his wife and son to disguise the lowered dopamine changes.
Clara manages to confront her husband as he is leaving the station, telling him about his son David's nightmares. Alex leaves, but then overrides his programming and detours from his current case to go to his house. He reviews the CCTV footage of his accident and realizes that David saw his body and was traumatized by it. Alex pursues Vallon for revenge, and in the course of tracking him down to a warehouse, learns Vallon is tipped off that Alex was coming and prepares for him, when Alex arrives Vallon nearly succeeds in killing him but fails and is shot by Alex. At the station Alex arrests the two corrupt cops, and is about to arrest the Chief of Police, when Mattox shuts him down by remote control, and Alex is taken back to OmniCorp.
Sellars decides to spin this turn of events to his advantage, via television presenter Pat Novak (Samuel L. Jackson), who thanks RoboCop for revealing the fallibility of the police, and points out that drones are incorruptible. A repeal of the Dreyfus Act goes underway, with votes overwhelmingly in support of the repeal. Clara goes to the press and angrily demands to see her husband. Sellars, seeing Alex is no longer useful and fearing the truth what has been done to him being exposed, orders Mattox to kill him. Norton reaches the lab first and revives Alex, telling him everything. Alex, feeling betrayed, goes after Sellars.
Sellars has the OmniCorp building shut down and armed with drones. Alex gains entry with the help of his former partner, Jack Lewis (Michael K. Williams) and other police officers. Alex reaches the roof, where Sellars is waiting for a helicopter and has Clara and David as hostages. Alex's programming prevents him from arresting Sellars, but he manages to overcome to shoot Sellars, killing him.
OmniCorp's parent company, OCP, decides to review the drone and RoboCop program. The President vetoes the repeal of the Dreyfus Act based on the testimony of Norton, who confesses everything they'd done in the RoboCop program. Alex's body is rebuilt in Norton's laboratory, and then he waits for Clara and David, who are coming to visit him.