When Garry Monahan was selected first overall by the Montreal Canadiens in the 1963 NHL amateur draft, he became the first-ever draft pick in NHL history. Born in Barrie, Ontario, Monahan played 12 seasons in the NHL with the Montreal Canadiens, Detroit Red Wings, Los Angeles Kings, Toronto Maple Leafs, and Vancouver Canucks.

After being selected by Montreal, he played junior A with the Peterborough Petes in the Ontario Hockey Association. In his final junior year, he turned into a top scorer playing on a line with Mickey Redmond, the league's leading goal scorer. Monahan scored 30 goals and 84 points in 47 games on what was otherwise a weak Petes team.

He made his NHL debut with the Canadiens in the 1967–68 season, but spent most of the year with Montreal's Central Hockey League affiliate, the Houston Apollos. After spending almost the entire 1968–69 season in the AHL, Monahan was traded to the Detroit Red Wings in June. Monahan saw little ice time and struggled offensively and before the end of the season was traded to the Los Angeles Kings. Before the next season, Monahan was dealt to the Toronto Maple Leafs. Monahan saw much more ice time in Toronto as a defensive forward, playing four full seasons with the Leafs. After the first game of the 1974–75 season, he was traded to the Vancouver Canucks and played there for four years, scoring his NHL career high of 18 goals and 44 points in the 1976–77 season. After his offensive numbers dropped off in his final year in Vancouver, Monahan rejoined the Leafs for the 1978–79 season, scoring just four goals in 62 games. That ended his career in the NHL, where he played 748 games over 12 seasons.

Hockey eventually took Monahan to Japan, where he absorbed a new culture for three seasons while skating for a company team in Tokyo, before he returned to a business life in Vancouver. He retired a few years ago from a career in real estate, having done radio work for the Canucks and been involved in stock brokerage.