Born in Toronto, Ontario, Jamal Mayers played Junior B hockey with the Thornhill Rattlers then was chosen 89th overall by the Blues in the 1993 NHL Entry Draft after his freshman year at Western Michigan University. He returned for three more years of college and reached double figures in goals each time. In 1996-97 he played six games for St. Louis but spent the bulk of his time developing with the AHL's Worcester Ice Cats.
Mayers began the 1998-99 in the minors but was recalled at mid-season and never looked back. A solid defensive player in the last 34 games of the season, he then looked confident in 11 post-season matches. In 1999-00 Mayers scored seven goals and played on the fourth line while helping the Blues finish at the top of the NHL's regular season standings. The next year he registered 21 points and was used in a variety of situations. Mayers was particularly solid in the playoffs when St. Louis advanced to the Western Conference final. He began the 2001-02 season as a valuable foot soldier on one of the league's elite franchises and was one of the team's more durable players, having only missed 13 games in his last three season. However, a serious knee injury would cut Mayers season short as the Blues had another strong season, the feisty forward was limited to only 15 regular season games.
On the international stage, Mayers represented Canada at the 2000, 2007 and 2008 World Championships.
On June 19, 2008, one day before the NHL draft, Mayers was traded to the Toronto Maple Leafs in exchange of a 3rd round pick in the 2008 NHL Entry Draft.
On January 31, 2010, Mayers was traded along with Matt Stajan, Niklas Hagman and Ian White to the Calgary Flames for Dion Phaneuf, Fredrik Sjöström and prospect Keith Aulie.
On August 4, 2010, Mayers was on the move again. This time as an unrestricted free agent he signed a one-year deal with the San Jose Sharks.
After a single season with the Sharks in which he compiled 124 penalty minutes in a largely checking role, the gritty winger was on the move again. This time, as a free agent, Mayers signed on with the Chicago Blackhawks.
Mayers would suit up in just 19 games for the Blackhawks during the lockout-shortened 2012-13 season. The Blackhawks would dominate NHL's regular season and capture the Presidents' Trophy.
The playoffs were more of the same for the Blackhawks and though pushed to the limit by the Detroit Red Wings in the second round, the Hawks would prevail and eventually earn the fifth Stanley Cup title in franchise history. Though he did not reach the NHL's minimum game requirements to have his name engraved on the Stanley Cup, the Blackhawks successfully petitioned the league and included Mayers in their 2012-13 engraving on hockey's most prized trophy.