Pete Stemkowski played his junior hockey in his hometown of Winnipeg from 1960 to 1962 when he went to Toronto to play for the Marlboros. He made his NHL debut with the Maple Leafs playing in one game that year. The next season saw Stemkowski split time with Toronto and their AHL affiliate in Rochester, but he spent the majority of his year with the big club the next season.
The 1966-67 season was Stemkowski's first full season in the NHL, and he helped the Leafs win the Stanley Cup. Midway through the next year, the Leafs traded Stemkowski to the Red Wings in a blockbuster deal that involved Frank Mahovlich, Garry Unger, Carl Brewer, Norm Ullman, Paul Henderson, and Floyd Smith. "Stemmer" played in the All-Star Game that year, and after three seasons in Detroit he was dealt once again, this time to the Rangers.
During his time in New York, the Rangers went to the semi-finals four straight years and to the Stanley Cup finals in 1972. That spring, they lost to the Bruins in six games. After seven years with the Rangers, Stemkowski became a free agent and signed with the L.A. Kings in 1977. He finished his NHL career in the 1977-78 season and played one final year in the AHL with the Springfield Indians before retiring.