Mahoney began his career as a trainee with Second Division club Fulham. Aged just 17 years and 38 days, he made his professional debut in a league match versus Cardiff City on 6 November 1976 and became the-then second-youngest Fulham debutant. He failed to break through to the first team at Craven Cottage, with his best seasonal record being 22 league appearances in 1980–81. Mahoney was released by Fulham in 1982 and made 69 appearances and scored 13 goals for the club.
Out of favour at Fulham, Mahoney joined Fourth Division club Northampton Town on loan in October 1981. He made six league appearances without scoring.
Brentford
Mahoney signed for Third Division club Brentford on a three-month trial in July 1982. Partnering Francis Joseph up front, Mahoney had a good start to life at Griffin Park, scoring 15 goals in his first 28 appearances and signing a permanent contract, before suffering a fractured leg in an FA Cup second round replay versus Swindon Town in December. After recovering, he failed to show the same kind of form and was released at the end of the 1983–84 season. Mahoney made 58 appearances and scored 19 goals during his two years with Brentford.
Crystal Palace
Mahoney joined Second Division club Crystal Palace in June 1984. In a one-season stay at Selhurst Park, he made 24 appearances and scored five goals.
Mahoney dropped into non-league football to sign for Isthmian League First Division club Grays Athletic in 1985. He was part of the team which secured promotion to the Premier Division and won two cups during the 1987–88 season, with Mahoney's striker partnership with Micky Welch being regarded as the most-feared in non-league football.
Mahoney signed for Essex Senior League club Canvey Island in 1989. He was a part of a golden era for the club, which saw the Gulls rise from the Essex Senior League to the Isthmian LeagueFirst Division with three promotions in three seasons. Mahoney was also part of the Canvey Island team which went on a run to the first round proper of the 1995–96 FA Cup, when they took Second Division club Brighton & Hove Albion to a replay before going out.
International career
Mahoney represented England Youth at international level.
Personal life
Mahoney's son, Tony Jr, was fatally stabbed in September 1999.
