He played junior hockey for the Windsor Spitfires in 1975-76. Kotsopoulos then entered Acadia University and sat out the 1976-77 season and played in 1977-78. Undrafted by any NHL team, he played two seasons in the minors before the New York Rangers signed him in 1980. Kotsopoulus debuted in the NHL with 16 points in 54 games and a good physical style. Kotsopoulos signed as a free agent with the Detroit Red Wings in 1989. After playing only 2 games with the Wings and spending some time with the Adirondack Red Wings, he retired in 1990. In 479 NHL games, he scored 44 goals and 109 assists.