Except for the eastern hoolock (Hoolock leuconedys), all gibbon species are regarded as critically endangered or endangered. The rediscovery of the Cao vit gibbon (Nomascus nasutus) in 2002 was exciting news for gibbon conservationists. However, its importance was hindered by disputation of its species status. Herein, we review the taxonomy, ecology and conservation of N. nasutus since its rediscovery. Morphology, vocalisations and genetic evidence suggests that N. nasutus is a distinct species from the western black-crested gibbon (N. concolor) and Hainan gibbon (N. hainanus). There is one confirmed population of approximately 120 individuals in a small karst forest along the China–Vietnam border. Although their habitat has been degraded by human activities, they have adapted behavioural strategies to life in karst forest, and reproduction has been successful. Two reserves have been established in both Vietnam and China, and no hunting has been reported. Besides goat grazing, human disturbances have largely been eliminated or controlled. Successful transboundary conservation interventions have contributed to this population’s slow increase despite it approaching its habitat carrying capacity. Habitat restoration is a priority for this species’ conservation. Future research directions include long-term population monitoring, karst forest restoration, impacts of human disturbances, and intra- and inter-species food competition.