Eastern grey kangaroos are widespread on the east coast of Australia and frequently reach high densities in reserves and parkland near urban areas. Management of these populations is highly contentious and non-lethal fertility-control technologies are sought as an alternative option to manage population size. This study evaluated the potential of slow-release gonadotrophin-releasing hormone agonist (deslorelin) implants to inhibit reproduction in female kangaroos. Deslorelin treatment effectively inhibited reproduction in adult females for periods of 559 ± 111 days (n = 6) and 651 ± 21 days (n = 5) after administration of one or two 10-mg implants respectively. Animals treated with the lower dosage tended to resume breeding earlier than those that received a total of 20 mg of deslorelin (minimum duration of 18 months). Deslorelin treatment had no effect on blastocyst reactivation in a single treated female and repeat treatment had no negative side-effects. This study has demonstrated that slow-release deslorelin implants can successfully inhibit reproduction for extended periods in the female eastern grey kangaroos. This approach may have potential application in reproductive management of problem kangaroo populations.