Forbes turned pro in 1996 at the age of nineteen, and ran off fourteen consecutive wins to begin his career before losing on March 11, 2000 against former WBC Featherweight champion Alejandro González.
On August 18, 2002, he lost the title when he could not make weight for a fight against David Santos, whom Forbes had previously beaten for the USBA belt.
On the ESPN reality show "Contender Season 2" series debut, Forbes was chosen to be on the Gold Team.
Forbes won his first three bouts of the series, defeating Freddy Curiel, Nick Acevedo, and Cornelius Bundrage, but he lost to Grady Brewer in the final match.
Forbes was defeated by Oscar De La Hoya on May 3 in Carson, California at the Home Depot Center by unanimous decision.