He played junior hockey for the Regina Pats from 1967 to 1969. The Detroit Red Wings picked him 21st overall in the 1969 NHL Amateur Draft. The Wings assigned him to their Farm team the Fort Worth Wings.
From 1970 to 1973 Garwasiuk played for the Providence Reds of the American Hockey League (AHL). After playing for the Sharks in 1973-74, scoring 6 goals and 13 assists in 51 games, Garwasiuk joined the AHL's Rochester Americans. He played for them until his retirement in 1980.