Although there is a growing recognition that the transfer of diseases between humans and non-human primates can be of great significance for conservation biology, there have been only a few studies focusing on parasites. In this study, saddleback (Saguinus fuscicollis) and moustached tamarin (Saguinus mystax) from the rainforest of the Peruvian lowlands were used as models to determine helminth parasite associations between canopy-dwelling primate species and a nearby human settlement. The human population showed high prevalences of infestation with a number of nematodes, including Ascaris lumbricoides (88·9%), Trichuris trichiura (37%) and hookworms (55·6%). However, the ova of these geohelminths were not detectable in tamarin faeces. Thus, no direct parasite transfer from humans to non-human primates could be documented. However, tamarin groups with more frequent contact to humans and their facilities had significantly higher prevalences and egg output of Prosthenorchis elegans, an important primate pathogen, than a forest group. In contrast, a cestode was significantly more common with more egg output in sylvatic than in human-associated groups. Human alteration of the habitat is likely to play a major role in determining the occurrence, prevalence and intensity of helminth infestation of wild non-human primates.