A native of Los Angeles, Nahan moved at age 2 with his mother to Canada, where he grew up playing ice hockey.

A star goalie at McGill University in Montreal, he signed a contract with the Toronto Maple Leafs of the National Hockey League in 1946.

Aside from the Rocky series, Nahan made a brief appearance in Fast Times at Ridgemont High (1982), in which he interviews the character Jeff Spicoli (Sean Penn) in a dream sequence; this scene was parodied in "Chuck Versus Tom Sawyer" with a fictional "Stu Brewster" (portrayed by Bill Lewis).

He played a small but vital role in the Rocky films as the play-by-play commentator who called all of the fictional boxer's title bouts.

Nahan's voice was used for the play-by-play in the computer boxing game that helped spark the title character's comeback in the sixth film of the series, Rocky Balboa.