Timneh Parrots Psittacus timneh are a threatened species endemic to the moist forests of West Africa. In 2016, they were categorised as ‘Endangered’ on the IUCN Red List, due to suspected rapid population declines driven by habitat loss and heavy trapping for the pet trade. Systematic assessments of the status of populations are lacking for much of their range and addressing this knowledge shortfall has been identified as a priority action. We combined multiple research approaches to investigate the distribution, trends and threats to Timneh Parrots in Guinea Bissau, where the species is restricted to the islands of the Bijagós archipelago and Pecixe. Direct observational surveys were conducted along line transects on 19 islands. A total of 69 groups were observed on eight of these islands, with the majority (78%) seen on just two islands. Forty-two interviews were conducted with local community members on 24 islands. Interviewees reported the species to occur on 20 islands and that populations are generally perceived to have declined in recent decades. Based on these findings and existing data we conclude that Timneh Parrots occur on 22 of the 32 islands considered and estimate the national population in Guinea-Bissau to be in the order of several hundred individuals, with perhaps half of the parrots occurring on the islands of João Vieira and Meio. Investigations into the factors linked to inter-island variation in parrot densities indicate that densities are highest on the islands which are most remote from permanent human settlements. These findings suggest that human activities including habitat modification and trapping have been important in driving population declines in Guinea-Bissau. We consider the implications of these findings for the conservation of Timneh Parrots.