The yellow-tailed woolly monkey ( Lagothrix flavicauda) is Critically Endangered and endemic to a small area of the Andean forest in northern Peru. I collected data on the home ranges, daily path lengths, diet and habitat use of two groups of L. flavicauda. Group follows took place at La Esperanza, Amazonas department, for 15 months between October 2009 and February 2011. The study site comprised a matrix of disturbed primary and regenerating secondary cloud forest. Home ranges were between 95 and 147 ha using 95 % minimum convex polygons, and home range overlap between the two groups was 1.6 ha. The range used by both groups varied between the wet and dry seasons. Daily path lengths were between 1.03 and 1.2 km. Fruit was the most commonly consumed dietary item followed by leaves and insects; a total of 16 plant resources were identified. There was a significant increase in consumption of leaves and insects during the dry seasons. Both groups used a variety of habitats but were only occasionally observed to use areas of white-sand forest. Home range and daily path length estimates are similar to results from studies of other woolly monkeys ( Lagothrix spp.), although home ranges were among the smallest recorded for woolly monkeys. L. flavicauda at La Esperanza are less frugivorous than Lagothrix spp., and the estimates here are lower than those from the previous preliminary work at this site. My results suggest that L. flavicauda are able to survive in disturbed habitat with small home ranges and at high group densities. More research is urgently needed at other sites with different ecological conditions to enable proper conservation planning and actions.