He is the son of former NHLer Bill McCreary Sr., nephew of former NHLers Keith McCreary and Ron Attwell, and cousin of former NHLer Bob Attwell and NHL referee Bill McCreary. His son, William "Bill" McCreary III, is currently a Federal Hockey League ice hockey player for the New Jersey Outlaws.
Bill McCreary Jr. was drafted in the 6th round, 114th overall, by the Toronto Maple Leafs in the 1979 NHL Entry Draft. He played two seasons of hockey for the Colgate University in the NCAA before signing a contract with the Toronto Maple Leafs in June 1980. He then split the 1980–81 season between the New Brunswick Hawks of the AHL and the Maple Leafs. He played 61 games in the AHL and 12 in the NHL with the Leafs that season. In those twelve games, he scored one goal, had no assists, and added four penalty minutes. That would be the extent of his NHL playing experience as he played out the rest of his career in the CHL, IHL, and AHL. He retired following the 1987–88 IHL season.
Bill McCreary is most remembered for his open ice hit on Wayne Gretzky on January 3, 1981. The hit was remarkable because it was the first time that Gretzky had been hit hard in his young career and it left Gretzky on the ice for several minutes. The myth that McCreary never played another shift in the NHL is false - the January 3 game was McCreary's 2nd game in his 12 game NHL career.