Harbour began acting professionally on Broadway in 1999, in the revival of "The Rainmaker". He then made his television debut that same year in an episode of "Law & Order", playing a waiter. He appeared again in 2002 in an episode of "", playing a child murderer. Harbour portrayed the recurring role of MI6 Agent Roger Anderson in the ABC series "Pan Am". In 2005, he was nominated for a Tony Award for his performance in a production of "Who's Afraid of Virginia Woolf?".