Dempsey spent most of his time with the Leafs's AHL affiliate St. John's Maple Leafs. During his time there, Dempsey was able to win the Fred T. Hunt Memorial Award for best exemplifying sportsmanship, determination and dedication in 2001–02. Aside from North American leagues, Dempsey has also played for Eisbären Berlin of the Deutsche Eishockey Liga (DEL) during the 2004–05 NHL lockout and SC Bern of the National League A (NLA). After his time with SC Bern was done, he retired from playing professional ice hockey in 2008.