Ellis was selected with the 40th overall pick in the 2005 NBA draft by the Golden State Warriors. He appeared in 46 games as a rookie and made three starts, with all three coming over the last four games of the season. He averaged 6.8 points, 2.1 rebounds and 1.6 assists in 18.1 minutes per game. In the Warriors' season finale on April 19, 2006, Ellis scored a season-high 27 points as Golden State lost 105–102 to the Utah Jazz.