Wambaugh's unique perspective on the realities of police work comes from experience: he is a former Los Angeles police officer and detective (later detective-sergeant) who served with the LAPD from 1960 until 1974. In 1970 his first novel, The New Centurions, was published to critical acclaim and popular success. (The success of the early books happened while Wambaugh was still working in the detective division. He reportedly remarked "I would have guys in handcuffs asking me for autographs.") Soon turning to writing full-time, Wambaugh was prolific and popular starting in the 1970s, mixing novels (The Blue Knight, The Choirboys, The Black Marble) with non-fiction accounts of crime and detection a.k.a. "true crime" (The Onion Field). Later books included Glitter Dome (a TV-movie adaptation starred James Garner and John Lithgow), The Delta Star, and Lines and Shadows.

In contrast to previous, heroic fictional policemen, Wambaugh brought a gritty texture to his flawed police characters. Many of his books were made into feature films or TV-movies during the 70's and 80's. The Blue Knight, a novel following the approaching retirement and last working days of aging veteran beat cop "Bumper" Morgan, was made into an Emmy-winning 1973 TV-made film starring William Holden, and later a short-lived TV series starring George Kennedy. His realistic approach to police drama was highly influential in both film and television depictions (such as Hill Street Blues) from the mid-70's onward.

Wambaugh was also involved with creating/developing the NBC series Police Story, which ran from 1973 to 1977. The anthology show covered the different aspects of police work (patrol, detective, undercover, etc.) in the LAPD with story ideas and characters supposedly inspired by off-the-record talks with actual police officers. At times the show's characters also dealt with problems not usually seen or associated with typical TV cop shows, such as alcohol abuse, adultery, and brutality. The show also had a brief revival on ABC during the 1988-1989 season.

Wambaugh was also involved in the production of the acclaimed film versions of The Onion Field (1979) and Black Marble (1980), both directed by Harold Becker. This was after The Choirboys film adaptation had met with very poor critical and audience reception a few years earlier. (Trivia note: all three films featured performances by then young up-and-coming actor James Woods.)

In 1992, Wambaugh suffered some controversy with his non-fiction book Echoes In The Darkness, regarding the murder of Susan Reinert, a teacher in Upper Merion School District outside Philadelphia, Pennsylvania. It was alleged that the author paid prosecutors in the trial of principal Jay C. Smith to funnel information to him before an arrest was even made. Smith was eventually released due to these allegations.

Wambaugh's most famous and recent non-fiction book is The Blooding, which tells the story behind how an early landmark case involving DNA fingerprinting helped solve two murders in the English Midlands, resulting in the arrest and conviction of Colin Pitchfork.