Before turning professional, he was a member of the 1980 Winter Olympics United States national team that upset the Soviet Union in the "Miracle on Ice" game.

Three days before the Olympics, in an exhibition match against the Soviet Union, O'Callahan injured his left knee.

He finally made the Blackhawks roster in 1982 and played there until 1987 when the Hawks left him unprotected for the 1987 NHL Waiver Draft.

He also made a final appearance for the United States national team at the 1989 Ice Hockey World Championship tournament.

In a 1981 TV movie about the gold medal-winning U.S. hockey team called Miracle on Ice, O'Callahan is played by Peter Horton.