Born in Le Roy, Minnesota, Mahoney was a right-hander who stood 6 feet 1 inch (1.85 m) tall and weighed 185 pounds (84 kg).

After the third, when he went 20–7 for the Class A Omaha Cardinals of the Western League,[1] he was selected by the White Sox in that off-season's Rule 5 draft.

He was effective in his first two outings, but in the third, on May 13 at Comiskey Park, he permitted a grand slam home run to Al Rosen of the Cleveland Indians in a lopsided, 11–2 defeat.

In perhaps his best overall performance, on June 29, 1951, against his former team, the White Sox, he threw 62⁄3 innings in a mop-up role, allowed two runs on four hits, and collected two singles in three at bats at the plate.

[3] In his 36 big-league games, Mahoney permitted 99 hits and 50 bases on balls in 902⁄3 innings pitched, with 34 strikeouts.