Dellorusso was drafted in the fourth round, 42nd overall, of the 2006 MLS SuperDraft by FC Dallas. He spent part of his first season on loan with Minnesota Thunder of the USL First Division. In 2007, his second year with the team, Dellorusso made his first career MLS start on October 20, 2007 against the Kansas City Wizards in a 2–0 loss. He played the entire 90 minutes of the game at the right back position and would be his only MLS start of the 2007 season. During the 2008 MLS season, Dellorusso was promoted to the senior roster on May 7, 2007 replacing retired defender Alex Yi. He made eight regular season appearances with FC Dallas, starting one game on September 4, 2008 against the Colorado Rapids in a 1–0 loss.