Coleman was raised in a foster home in Richmond, Virginia. As a youth, he participated in track and field, but turned his attention to studying drama after a leg injury. He attended Virginia Commonwealth University on a scholarship for his freshman year, before dropping out to serve in the United States Army. During his time in the army, from 1995 to 1999 he worked as a video cameraman.
Coleman had a starring role on the HBO series The Wire as reformed Criminal Dennis "Cutty" Wise. In 2002, Coleman starred as O.J. Simpson in TNT's television movie Monday Night Mayhem.
Coleman also had a guest role in the Terminator: Sarah Connor Chronicles TV series on Fox. He also had a small role in Carlito's Way: Rise to Power. Coleman was also involved with the development of Left 4 Dead 2, as a voice actor for the character Coach. In 2009, Coleman appeared in a revival of August Wilson's play Joe Turner's Come and Gone on Broadway and also had a starring role in the Norwegian TV series Buzz Aldrin, What Happened To You In All The Confusion?, based on the novel by Johan Harstad. The series aired in Europe in November 2011.
He guest starred in the In Plain Sight episode "Whistle Stop" as an ex-boxer/witness suffering from pugilistic dementia, and in the Lie to Me episode "The Canary's Song" as a coal miner. He was also a guest star in two episodes of It's Always Sunny in Philadelphia in 2010, and one in 2013. In 2011, he began playing Gary Miller, the ex-husband of Nikki Miller and father of manipulative daughter Mackenzie, in the Fox television sitcom I Hate My Teenage Daughter.
From late 2012 to early 2015, Coleman played Tyreese on AMC's post-apocalyptic horror series The Walking Dead. In the third season, Tyreese was a recurring character. Coleman was upgraded to series regular and main cast member at the start of the fourth season and retained this status for its fifth season until his character was killed off in the mid-season premiere. On November 20, 2014, he was announced to play Fred Johnson, a.k.a. "The Butcher of Anderson Station", a former Marine caught in a power struggle between Earth and Mars on the Syfy science-fiction series The Expanse. Coleman has taken on a main role in the 2015 series, and returns in Season 2.
On May 1, 2015, Coleman was recorded in the middle of a rant on New York City's 4 subway train. Coleman stated that the rant was prompted by "built-up frustration" stemming from the death of Freddie Gray in Baltimore.
In 2016, he played the role of Tobias Church on Arrow. Currently, he is playing the role of Klyden, Second Officer Bortus's mate, on The Orville.
