Endemic to the Atlantic forest of the Brazilian states of Sergipe and Bahia, Callicebus coimbrai survives in a highly fragmented landscape characterized by small remnants of forest in a matrix of plantations and pasture. First described only seven years ago, the species is still poorly known and, until the present study, had been recorded from only fifteen sites in Sergipe, in fragments of no less than 40 ha. Here, we report on a survey of the presumed range of the species in Sergipe, with the primary aims of identifying remnant populations and evaluating the influence of factors, such as fragment size, on survival. Populations of C. coimbrai were recorded through either sightings or response to playbacks of vocalizations at 30 of 147 sites surveyed (including 15 confirmed previously), and consistent reports from local residents were obtained at a further 46 localities. Six of the confirmed fragments were less than 20 ha, including one of only 3 ha. This indicates that the species is relatively tolerant of habitat fragmentation, and is able to survive in isolated forests of small size. Together with the growing number of known (and potential) populations, this tolerance is a positive factor for the long-term conservation of the species. However, based on the results of this survey, estimates of the total area of forest occupied by the species, and numbers remaining in the wild are only 100–150 km² and 500–1,000 individuals, respectively. Clearly, this situation requires urgent measures, including the implementation of protected areas and provisions for metapopulation management.