ABSTRACT: The global biodiversity crisis particularly affects freshwater fishes. Currently, 20% of Australia’s highly endemic freshwater fishes are formally recognised as being of conservation concern under national, state and territory listings. Four of the 5 described species of Nannoperca (Percichthyidae) are threatened with extinction, with N. oxleyana Whitley listed as endangered under Australian legislation and internationally by the IUCN. National recovery planning has commenced with the objective of returning this species to a position of ‘viability in nature’ in New South Wales (NSW) and Queensland. This paper describes the conservation biology of N. oxleyana, providing a case history for a small species of no commercial importance threatened by the classical triumvirate of habitat degradation and loss; small, declining and fluctuating populations driven more by environmental conditions than demographic forces; and the effects of introduced species. A process for declaring critical habitat for N. oxleyana has commenced in NSW. Habitat protection involves managing threats, including run-off originating from unsealed roads, herbicide use, fire management activities and disturbance by recreational users such as 4-wheel drivers and campers. Information on the distribution and breeding patterns of N. oxleyana has been provided to local and state government authorities to assist in managing drainage and development schemes that might impact N. oxleyana habitat. Monitoring has confirmed the persistence of many N. oxleyana populations in both jurisdictions.