Born in Omaha, Nebraska, Gibson overcame childhood illness to excel in youth sports, particularly basketball and baseball. After briefly playing under contract to both the Harlem Globetrotters basketball team and the St. Louis Cardinals organization, Gibson decided to continue playing only baseball professionally. He became a full-time starting pitcher in July 1961 and earned his first All-Star appearance in 1962. Gibson won 2 of 3 games he pitched in the 1964 World Series, then won 20 games in a season for the first time in 1965. Gibson also pitched three complete game victories in the 1967 World Series.