Harrison was drafted by the Toronto Maple Leafs in the third round, 82nd overall, of the 2001 NHL Entry Draft. After spending four seasons in the American Hockey League (AHL) with Toronto's farm team, Harrison made his NHL debut on January 27, 2006, against the Montreal Canadiens, in which he registered his first NHL career point, coming in the form of an assist. On June 16, 2008, Harrison signed a one-year contract with EV Zug of the Swiss National League A, but on March 27, 2009, he returned to the Toronto Maple Leafs, signing a deal, pro-rated at $475,000, to play out the rest of the 2008–09 season.