Sullivan played 1,011 NHL games for the New Jersey Devils, Toronto Maple Leafs, Chicago Blackhawks, Nashville Predators, Pittsburgh Penguins and Phoenix Coyotes, after the Devils selected him in the ninth round (No. 233) of the 1994 NHL Draft. Prior to joining the League for 16 games of the 1995-96 season, Sullivan had 81 points (31 goals, 50 assists) in 75 regular-season games for Albany of the American Hockey League and 11 points (four goals, seven assists) in 14 Calder Cup Playoff games to help the River Rats win the league championship.

Sullivan played four seasons for the Maple Leafs following a trade from the Devils on Feb. 25, 1997. He set NHL career highs in goals (34) and points (75) with the 2000-01 Blackhawks and enjoyed his formative seasons after Chicago sent him to Nashville on Feb. 16, 2004. He had 30 points (nine goals, 21 assists) in 24 games following the trade, including a hat trick in his first game, and helped the Predators reach the Stanley Cup Playoffs in four of his six seasons. He was awarded the 2009 Bill Masterton Memorial Trophy for his perseverance, sportsmanship, and dedication to hockey after returning from a near two-year absence because of a back injury.

Sullivan finished his NHL career with the Penguins, Coyotes and a return to the Devils, who acquired him from Phoenix on April 3, 2013.