The Grande Comoro Scops Owl (Otus pauliani) is an endangered, rare and elusive owl species restricted to the Karthala forest, Grande Comore. This scops owl species is listed among the most threatened animals of the Comoro archipelago. The species is subjected to strong anthropogenic pressures causing a high rate of habitat loss. Little is known about the species' population size, habitat suitability and geographic distribution, making the establishment of relevant conservation strategies difficult. In this study we assessed the population density and abundance of the species using the distance sampling approach through (1) the conventional distance sampling method (CDS), and (2) density surface modeling (DSM). Based on DSM, we applied a species distribution modeling method to investigate habitat suitability and geographic distribution of the species to close this knowledge gap. Average population density was estimated to be ca. 27 individuals km(-2). We estimated a global population size of 3452 individuals. Our DSM suggested that the Grande Comoro Scops Owl has a very limited distribution (133 km(2)), restricted to high elevations in Grande Comore's remaining natural forests (between 800 and 2000 m altitude). However, the currently high level of habitat disturbance and conversion of natural forest into agricultural land could render the species vulnerable to extinction. To ensure the viability of the species and the biodiversity of the Karthala forest, we suggest (1) restoring forest and securing corridors in the Karthala remnant forest; (2) avoiding the conversion of secondary forest into agricultural land, and using existing agroforestry for plantation development; (3) involving a broad community of local individuals and entities in their conservation and management.