Amongst the teams Mallen played for were the Calumet Miners, Pittsburgh Lyceum, Pittsburgh Bankers, Toronto Professionals and Galt Professionals. Jim Mallen was a small player in stature even for his era but stocky built at 5"5" and approximately 165 pounds. He played primarily at the center and rover positions.
When with the Galt Professionals Mallen twice was on a team that challenged for the Stanley Cup, in January 1910 and in March 1911, but the Galt team lost both times to the Ottawa Senators. His younger brother Ken Mallen also played professional ice hockey and was on the 1915 Vancouver Millionaires team that won the Stanley Cup.
