McCreary first refereed an NHL game in 1984. On February 16, 2008, McCreary refereed his 1,500th NHL game in the game between the Toronto Maple Leafs and the Boston Bruins. McCreary wears uniform number 7 since the 1994–95 NHL season, and has been wearing a helmet for most of his refereeing career. McCreary has a pregame ritual in which he flips the puck in the air before dropping it for the opening faceoff.
During the 2002 Winter Olympic Games in Salt Lake City, he officiated the men's hockey gold medal game won by Canada vs USA by the score of 5-2.
During the 2004–05 NHL lockout, McCreary worked building kitchen cabinets to make ends meet.
In 2007, McCreary was selected to officiate the Stanley Cup Finals for the 13th year in a row. McCreary was not selected to work the Stanley Cup Finals in 2008. In 2009, McCreary officiated the Stanley Cup Finals for the 14th time. He was also selected as one of 13 NHL referees to officiate at the 2010 Winter Olympics in Vancouver, including the Gold Medal Game. He will retire as an NHL referee at the end of the 2009-10 NHL season.