Summary We applied an adaptive management approach to reduce extinction risks faced by a disjunct and ecologically significant population of Black Cypress Pine (Callitris endlicheri), listed as an endangered population on the New South Wales Threatened Species Conservation Act 1995. In summer 2001–2002, an unplanned fire burnt the population, resulting in mortality of most standing plants. Concerns were raised about the potential impact of herbivores, particularly feral Rusa Deer (Cervus timorensis), on the recruitment of post-fire seedlings that might replace the loss of fire-killed standing plants. We applied an adaptive management approach to detect trends in the population following the fire, and to evaluate and trial in situ management options for mitigating threats to the remaining plants. Post-fire monitoring detected continuing declines in both the remaining adult population and the post-fire cohort of seedlings, and identified browsing by Deer as a serious and ongoing threat to the population. We designed a controlled experiment, with the aid of natural and artificial ‘nurse plants’ to assess the effects of herbivore exclusion on seedling growth and survival, and to test for differences in those effects under alternative management strategies. The experiment was designed and implemented with little cost other than field time and with logistic constraints on replication. By protecting exposed seedlings from browsing using woody debris, we were able to significantly increase seedling growth and survival, and to quickly arrest the population decline. Our results suggest that excluding Deer from the population by more permanent means will have a significant positive effect on its long-term persistence. Our case study demonstrates the utility of adaptive management approaches in threatened species conservation, their feasibility even under severe budgetary and logistical constraints, and how ongoing monitoring and experimentation are crucial for successful management of biodiversity.