Islands are often characterized by high biodiversity and species endemism that is strongly threatened by a range of processes, especially habitat loss and invasive species. Compared to the mainland, islands are often understudied, making conservation management challenging. Pterocymbium oceanicum (local names Yanita or Ma) is a Critically Endangered tree species endemic to Fiji. However, little is known about its distribution and ecology, nor is the species formally protected in situ or ex situ. We undertook an intensive field-based survey to collect and collate information on population size, distribution, phenology, species ecology and current threats to guide the development of a management plan. Compared to the latest (2016) IUCN Red List assessment, we found that the species occurs in more than twice as many locations (a total of nine) and that its estimated global population size is more than six times larger (1670+ ct. < 250). We also for the first time collected seeds and described their morphology, found evidence of color polymorphism in flowers, and observed subpopulation variation in flowering and fruiting phenology. While this information is important for developing conservation strategies for Yanita, more research is needed to improve the population size estimate, evaluate population dynamics, confirm the flowering habits, identify the driver of the observed flower color polymorphism and address threats to the different subpopulations.