He was educated at St. Paul's Milagiriya and Royal College Primary before migrating to Australia with his family when he was aged nine. He studied at Camberwell Grammar School, Melbourne (where he is currently a member of the school board), received his MBBS degrees from the University of Melbourne in 1962, and his Doctor of Medicine (MD) degree from Monash University in 1969.
De Kretser is an infertility and andrology expert, and a long-serving academic. He began working at Monash University in 1965, in the university's department of anatomy, and has also worked as foundation director of the Monash Institute of Reproduction and Development (recently renamed the Monash Institute of Medical Research) and as Associate Dean of the Faculty of Medicine, Nursing and Health Sciences (the Biotechnology Department). He was a senior Fellow of endocrinology at the University of Washington in Seattle from 1969 to 1971.
He founded a medical research group, Andrology Australia. Among memberships of other professional groups, he is a fellow of the Australian Academy of Science On the nomination of Premier of Victoria Steve Bracks, he was appointed Governor of Victoria, taking office on 7 April 2006, succeeding John Landy. He left the post on 8 April 2011, and was succeeded by Alex Chernov.
Australian Academy of Science.