The Unit was based on Eric L. Haney's 2002 memoir Inside Delta Force: The Story of America's Elite Counterterrorist Unit, with Haney serving as producer and writer on the show he helped create alongside David Mamet and Shawn Ryan.

In a television interview, series creator Eric Haney, a former Delta Force operator, stated that the term 'Delta Force' is never actually used within the special operations community, where it is only referred to as 'The Unit', with the official DOD designation being 'Combat Applications Group'.

Season 2, Episode 23 depicts an investigation into illegal activity by The Unit that closely mirrors the real-life investigation into SEAL Team 6 founding commander Richard Marcinko, who was prosecuted over $50,000 in purportedly embezzled cash despite his team regularly handling millions in unmarked bills.

The theme music for the first two seasons, 'Fired Up' by Robert Duncan, is actually an adaptation of a Marine Corps running cadence called 'Fired Up, Feels Good', despite the show focusing on an Army special ops unit; Duncan later created a new 22-second theme called 'Walk the Fire' for seasons three and four.

The fictional base of Fort Griffith is depicted with numerous Missouri references, including Greenwood-area police cars and Missouri license plates in many episodes, yet a red, white, and blue Idaho license plate can also be spotted in almost every episode.

The Unit was cancelled by CBS on May 19, 2009 after four seasons and 69 episodes, but on that same day 20th Century Fox Television announced the show would continue in syndication reruns on stations covering 56% of the country, including Fox Television Stations.

Two tie-in novelizations, 'The Unit: Seek and Destroy' (2008) and 'The Unit: Lock and Load' (2009), were written by Patrick Andrews and published by Signet Books, featuring the show's main characters in missions not depicted in the CBS series.

Executive producer Shawn Ryan revealed in an interview that a planned but never-produced fifth season would have followed Jonas Blane's final mission and retirement due to combat stress and injuries, introduced a storyline where Sam McBride confides to Bridget Sullivan that he is the Unit's first gay member, and included the CIA creating a rival commando force as a mirror image of The Unit.