The following month at the 2012 World Short Course Championships in Istanbul, he won two medals in relay events. Alongside Tommaso D'Orsogna, Kyle Richardson and Kenneth To, they won the bronze in the 4 × 100 metre freestyle relay in 3:07.27. In the 4 × 200 metre freestyle relay event, Mahoney swam the third leg of the heats to qualify third fastest. In the final, Mahoney was replaced by Richardson and with D'Orsogna, Jarrod Killey and Robert Hurley won silver in a new Oceanian record time of 6:52.29. In his individual swims, Mahoney finished 7th in the 200 metre backstroke and narrowly missed the final in both the 400 and the 200 metre individual medley events