Mickoski started his National Hockey League career with the New York Rangers in 1947. He would also play for the Chicago Black Hawks, Detroit Red Wings, and Boston Bruins. He retired after the 1960 season. He played junior with the St. Catharines Falcons of the OHA in 1943-44 then spent two years in the Manitoba Junior Hockey League with the Canadian Ukrainian AC and the St. James Canadians. He bounced around the minors and senior leagues for a couple of years before joining the New York Rangers for two playoff games in 1948.