In 2003, as a true freshman at Florida State, Sims played in every single game. He finished ninth on the team in tackles and was one of the teams top special teams performers. In 2004, his sophomore year, Sims played in all 12 games, and started the final 11. For his exceptional play on the field in 2004, Sims was named to the second All-ACC team and ESPN named Sims to their first team All-American team. Expectations for his junior year were high, as The Sporting News and other publications named him to their pre-season All-American teams.