Simms played college soccer at East Carolina University from 2000 to 2003, where he appeared in 72 games and notched seven goals and seven assists.

Simms went undrafted by Major League Soccer after college and instead signed with Richmond Kickers of the A-League.

Although he had a relatively impressive first season with the Kickers and started 28 games for the club, Simms's talent was not really recognized until he was called into the United States national team camp as a replacement player due to a conflict between the United States Soccer Federation and the players in 2005.

Simms's performance in the national camp intrigued several MLS teams, and he was eventually signed as a discovery player by D.C. United on February 25, 2005.

After seven seasons with D.C. United, the club declined his 2012 contract option and he entered the 2011 MLS Re-Entry Draft.