He served as an assistant coach during the U.S. Project-40 squad's visit to Portugal, and continued his coaching duties with the Fire, becoming the senior assistant coach in 2001. Upon dismissal of former head coach Dave Sarachan, Hamlett received interim head coaching duties on June 20, 2007, but resumed assistant coaching duties following the arrival of Juan Carlos Osorio. When Osorio resigned take on the head coach job at the New York Red Bulls, Hamlett was hired as the head coach. Following Fire's failure to qualify for the 2009 MLS Cup, Hamlett was fired as head coach on 24 November 2009. Over his two-plus year tenure with the Fire, Hamlett helped the team to back-to-back Eastern Conference Finals, as well as the 2009 SuperLiga Final, going 24-18-21 in league play and 31-23-24 across all competitions.