Gerald Hay was born in Edinburgh, Scotland in 1946 before later moving to Australia, where he took up weightlifting. In 1964 Hay competed in the bantamweight class at the Tokyo Olympics, where he placed 21st with a total lift of 290.0 kg. Two years later he finished fifth in the same weight class at the British Empire and Commonwealth Games in Kingston, Jamaica. Hay returned to the British Commonwealth Games in 1974, winning silver in the featherweight in Christchurch, New Zealand, finishing just behind compatriot George Vasiliades.