The 2004 Calder Cup playoffs of the American Hockey League began on April 14, 2004. Twenty teams, the top five from each division, qualified for the playoffs. The fourth- and fifth-placed teams in each division played best-of-3 series in the qualifying round. The four winners, in addition to the other twelve teams that qualified, played best-of-7 series for division semifinals, finals and conference finals. The conference champions played a best-of-7 series for the Calder Cup. The Calder Cup Final ended on June 6, 2004 with the Milwaukee Admirals defeating the Wilkes-Barre/Scranton Penguins four games to none to win the first Calder Cup in team history. Milwaukee's Wade Flaherty won the Jack A. Butterfield Trophy as AHL playoff MVP.
Several league records were set during the 2004 Calder Cup Playoffs.
After the 2003–04 AHL regular season, 20 teams qualified for the playoffs. The top five teams from each division qualified for the playoffs. The Milwaukee Admirals were the Western Conference regular season champions as well as the Macgregor Kilpatrick Trophy winners with the best overall regular season record. The Hartford Wolf Pack were the Eastern Conference regular season champions.
In the qualification round all games are played at the arena of the fourth seed. In each round after the Qualification Round, the higher seed receives home ice advantage, meaning they can play a maximum of four home games if the series reaches seven games. There is no set series format for each series after the Qualification Round due to arena scheduling conflicts and travel considerations.