This is a list of fictional characters that have appeared in BBC One's science fiction/police procedural drama, Life on Mars, and the following series Ashes to Ashes.

DCI/DI Sam Tyler is played by John Simm in the original British version of Life on Mars and in the American version he is played by Jason O'Mara. The character of Sam Tyler is the main protagonist within the programme.

WPC/DC Annie Cartwright is portrayed by Liz White. During the first series of Life on Mars, the character was a Woman Police Constable serving in uniform. Early in the second series, DCI Gene Hunt allows her to join CID as Woman Detective Constable. Throughout both series, Cartwright helps the programme's protagonist, Sam Tyler adjust to life in the 1970. Cartwright is the only person in 1973 who Sam tells that he has travelled back in time, and she treats him sympathetically, believing that he is suffering from severe concussion after being hit by a car. During the first episode of series one, when Sam climbs onto the police station roof, considering suicide, Cartwright convinces him not to jump. Upon Sam first losing consciousness after the car accident which sent him back in time, he sees a fleeting image of a woman in a red dress running away from an attacker. The image is later revealed to be a childhood memory of Annie chasing after Sam's father, and being attacked by him. No references are made to Annie's family in either the first or second series, apart from a mention of an unnamed nephew in "The Crash", which indicates that she has a brother or sister.

In the US remake, Annie Norris (Gretchen Mol) is a uniformed policewoman with an undergraduate psychology education who has aspirations of making the detective squad. Norris constantly struggles against sexist attitudes about the role of a woman in police work. Owing to her gender, her nickname among the detectives is "No Nuts Norris". She is the only one on the force to whom Sam has revealed that he is from the future – although she does not seem to believe him, she is the most sympathetic of his colleagues; she puts more faith in his claim after a prophecy from Sam saves her life from Vic Tyler in the counterpart episode to the BBC's first series finale. She is promoted to detective in the finale.

DC/DS/DI Raymond Milton "Ray" Carling is portrayed by Dean Andrews.

Ray Carling is shown to be similar in character to his boss, DCI Gene Hunt. During Life on Mars, Carling often prefers Hunt's brutality and corruption over DI Sam Tyler's ideas. Carling has also been described by the BBC's website as Hunt's "right-hand man when it comes to fighting, shooting, gambling and the ladies". Throughout the series, Carling frequently clashes with Sam Tyler regarding his policing methods. It is revealed that Carling had applied for promotion to DI (Detective Inspector), but was passed over for the apparently transferred Sam Tyler, fuelling his grudge against Tyler. During episode 7 of the first series, Billy Kemble is arrested on drug-related charges. In an attempt to make him reveal his supplier, Carling and Chris Skelton force-feed Kemble cocaine, but Kemble has a heart attack and dies in police custody. After an extensive cover-up operation, Hunt angrily demotes Carling to DC (Detective Constable). After a period of time as a DC, Hunt re-promotes Carling to DS in series 2, episode 1, which he remains at for the next decade until 1983 in Ashes to Ashes.

During episode 3 of the second series, Carling is blown up by a car bomb and hospitalized. A short time before the explosion, Sam Tyler claims it is a hoax and not the IRA as he knows from 2006 that they never used dynamite. Carling believes Tyler and investigates, only to be caught in the explosion. He suffers severe post-traumatic stress disorder after his release from hospital and unwittingly compromises Tyler's investigations. He is, however, hailed a hero by the rest of CID. During series 2 he drove a Morris Marina.

Alongside Gene Hunt and Chris Skelton, Carling moved from Manchester to London and joined the Metropolitan Police shortly after the death of Sam Tyler in 1980. Despite Carling openly being racist and sexist during Life on Mars, he is consistently displayed to have an improved attitude throughout Ashes to Ashes. Unlike his disdain for DI Tyler in 1973, he forms a good working relationship with DI Alex Drake and, most of the time, fully respects her authority over him, despite her gender. During the third series in 1983, Carling is promoted to a DI while Hunt is on the run for Drake's shooting, and takes overall charge of CID. When Hunt returns with Drake, he hastily disregards and lampoons Carling's efforts, describing him as looking like a "maths teacher". Carling goes on to ruin a stake-out during a hostage situation, but after the case is solved, Hunt acknowledges that it was a difficult operation and finally applauds his ability and effort. It is also revealed that Ray's father and grandfather were in the army, but Ray never joined himself as he went out drinking on the night he was supposed to sign up and never got around to going because he was scared, his relationship with his father subsequently souring despite his successes in the force. In series 2 in 1982, Carling actually fills out an army application form, but when he asks Alex Drake to write a reference, she takes the form and rips it up into little pieces, convincing him to stay. Ray, along with Shaz and Chris, endures visions of stars and space and hears strange voices, like that of in a pub, and described by Chris as Nelson (Tony Marshall), the publican from Life on Mars, asking him what is he having to drink. Although he initially dismisses it as alcohol-related, he is eventually brought round by Shaz and the three of them share the vision together in the street outside Luigi's. He drives a MkII Ford Granada 2.8S.