Dunbar was born in Berkeley, California. He attended Oakland Technical High School, Oakland, California, Morehouse College, Atlanta, Georgia and graduated before moving on to study at the College of Santa Fe, New Mexico and the University of New Mexico.
Dunbar is well known for his leading role as Kenny Chadway on the television series Soul Food and he was named as one of Television's 50 Sexiest Stars of All Time by TV Guide. He landed a regular role as Benjamin Miles "C-Note" Franklin on the United States television series Prison Break. In 2007, Dunbar guest-starred on grey's anatomy as Mr. Brotherton in 2007, Dunbar starred on the short-lived TNT medical drama Heartland. He made a guest appearance on Noah's Arc as himself to give Noah (screenwriter and the main character of the show) some ideas about his movie Fine Art. He also had a recurring role on the UPN series Girlfriends and is also known for his role as "Pookie" on the television series The Game. He was also a regular on the short-lived FX series Terriers. Dunbar's other TV credits include guest appearances on Earth 2, Felicity, The Pretender, Two Guys and a Girl, and North Shore. In 2011 he joined the cast of FX's hit show Sons of Anarchy as the new Sheriff of Charming, Eli Roosevelt. In 2013, Dunbar joined the CBS crime drama The Mentalist as FBI agent Dennis Abbott. His film projects include Punks (which debuted at the 2000 Sundance Film Festival), Misery Loves Company, Sick Puppies, Whodunit, Dirty Laundry, All About You Kiss Kiss Bang Bang, and the Tyler Perry-produced film, "The Family That Preys". Dunbar has contributed to the art world through the mixed media exhibit, ARTHERAPY. Dunbar posed for the November 2003 issue of Playgirl magazine.