Alexander began his professional career in 2004 as a cruiser weight. Whilst he was undefeated, he would have lost a bout to Marty Lindquist in 2006 via a 1st round KO, however the bout was later declared a no contest because Lindquist failed a drug test. Although they would re-match and Alexander won by decision. His current professional record is 15 wins, 6 losses and 1 no contest.
On December 10, 2011, after a 2-year pause from boxing, Alexander fought the biggest fight of his career when he faced the boxing legend: Roy Jones Jr. for a vacant cruiserweight championship in what many assumed would be the boxing legends' last fight. Alexander lost by unanimous decision.