In 2004 and from 2006 to 2008, the Mammoth lead the league in attendance. 2006 was the first year in the 20-year history of the NLL that the league had an attendance of more than one million fans in one season. The Mammoth had the honor of hosting fan number one million. In 2008, the Mammoth average attendance per game was higher than Pepsi Center's other teams, the Colorado Avalanche (NHL) and the Denver Nuggets (NBA).
In the 2006 season, the Mammoth went to the playoffs in the #2 seed in the Western Division. Round one was hosted in Colorado against rivals Calgary. The Mammoth won 18-17 in overtime. Brian Langtry scored the overtime goal. Round two (Western Division finals) was also hosted at Pepsi Center against the Arizona Sting. Rookie Dan Carey scored the winning goal as the Mammoth defeated the Sting 13-12. The championship game was held at HSBC Arena in Buffalo against the Bandits who held the league's best record and the incumbent league MVP, goaltender Steve Dietrich . The Mammoth won the Champion's Cup by a score of 16-9, with Gavin Prout being named Game MVP.