The narrow-striped mongoose Mungotictis decemlineata is a small, endemic carnivore currently known to occur only in the dry deciduous forests of the central and southern Menabe regions of western Madagascar. It is categorized as Endangered on the IUCN Red List and is threatened by rapid habitat loss from deforestation. From live-trapping and village surveys we found M. decemlineata to be distributed throughout the largest area of connected forest in central Menabe and most of the larger forest fragments in southern Menabe. We estimated there are a minimum of 2,000–3,400 adults in central Menabe and 6,400–8,650 adults in southern Menabe. Although this represents the total known population, the southern limits of the species' range are still unclear. Fifty-four individuals were live-trapped in central Menabe. M. decemlineata abundance was not correlated with forest structure or invertebrate abundance and diversity at the sampled sites. The building of access roads for logging may have a long-lasting effect by increasing the level of human disturbance, predation by domestic dogs, and illegal cutting within the surrounding area. Conservation management efforts to save M. decemlineata need immediate implementation, with emphasis on cooperative efforts with local villages to reduce the rate of slash-and-burn agriculture and logging of the remaining dry deciduous forest of the region. Research to determine population trends and status of M. decemlineata south of the Morondava and Mangoky rivers is required.