Gentry later became an assistant coach for the Phoenix Suns for six years, serving under head coaches Mike D'Antoni and Terry Porter. When Porter was fired in his first season as head coach, Alvin Gentry took over on an interim basis. He was named Suns' head coach for the 2009-2010 season. Gentry's record in his first year as head coach during the 2009-2010 season was 54 wins, a career high, against 28 losses. The Suns advanced to the Western Conference Finals and lost to the Lakers in six games. He became the fifth head coach in franchise history to lead his team to a Western Conference Finals berth in his first full season. Gentry figured out how to blend the two styles of D'Antoni and Porter. Comparing his coaching to D’Antoni, Gentry said "We are not seven seconds or less. We’re 12 seconds or under. We don’t take a lot of really quick shots. We don’t play with that breakneck pace. We play with a rhythm." Spurs head coach Gregg Popovich remarked "One thing about Phoenix is they are better defensively than in the past. They’re much more active, much more committed, they’ve taken responsibility to a much more significant degree than ever before."