We studied the Black-fronted Piping Guan (Pipile jacutinga), a medium-sized cracid (1.5 kg), endemic of Atlantic rainforest and considered endangered. We present density estimates of Black-fronted Piping Guans derived from line-transect surveys (total effort  =  2,246 km) across 11 protected areas (6 continuous mainland areas, 3 non-connected mainland areas, and 2 inshore islands) in São Paulo State, southeastern Brazil. Both islands and the continuous mainland forests of Paranapiacaba massif had the highest density estimates of the species. The largest continuous mainland Atlantic Forest (Serra do Mar massif) had the lowest density estimates and the species was absent in some regions of this mountain range. All non-connected mainland forests also had low density estimates or absence of the species. Our data indicate the Black-fronted Piping Guan is not extremely sensitive to habitat disturbance and the major threat to its conservation is most likely from illegal hunting. The absence or low density estimates of the species in three survey sites is of special concern, because it is known guans are important in seed dispersal, which may have long-term consequences for forest regeneration.