Clarke MacArthur was born April 6, 1985 in Lloydminster, Alberta. Buffalo's third round choice in the 2003 NHL Entry Draft, MacArthur is a graduate of the WHL's Medicine Hat Tigers.
An offensively gifted centreman, MacArthur over three seasons with Medicine Hat would tally 224 points and be named to the 2004 Memorial Cup All-Star Team. He made his professional debut in the 2005 AHL playoffs with the Sabres' affiliate, the Rochester Americans. The following year MacArthur appeared in his first full pro season, recording 53 points in 69 games. In 2006-07, MacArthur led Rochester with 63 points in 51 games and made his NHL debut in a December 19 game against the Montreal Canadiens. His offensive output in Rochester also earned him a spot in the 2007 AHL All-Star Game.
On the international stage, MacArthur proudly represented Canada at the 2005 World Junior Championship winning a gold medal.
On March 3, 2010, the NHL trade deadline, MacArthur was sent to the Atlanta Thrashers in exchange for a pair of draft picks. He would finish the season with the Thrashers, appearring in just 21 games before testing the free agent market the following summer. On Auguest 28, 2010 he inked a one-year deal with the Toronto Maple Leafs.
MacArthur played in three seasons in Toronto when he left as a free agent to sign a two year contract with the Ottawa Senators.