Harvestmen show a high degree of endemism in the Atlantic Rain Forest (eastern coast of Brazil). This biome shows the highest diversity of harvestmen inhabiting Brazil; 2/3 of the species are found in this area. Most of the species are distributed in a few thousand square kilometers, almost always within one mountain range. The similarities of 26 localities were studied, including sites from the Brazilian savanna, using data from recent collections (more than 8,000 specimens) and published data. A cluster analysis using Sørensen´s Coefficient indicated a high degree of endemism of species of harvestmen (similarity indexes below 0.5). It resulted in six main clusters related to the large mountain ranges and near sites. A high variation in richness was observed; 4–64 species per locality. The distribution of 84 species of four recently reviewed subfamilies of Gonyleptidae (Goniosomatinae, Caelopyginae, Progonyleptoidellinae and Sodreaninae) was studied. Eleven areas of endemism, with 3–14 endemic species each, were proposed. A primary Brooks Parsimony Analysis showed a possible first vicariant event splitting the fauna of two northern areas from the rest, and a second event splitting the fauna of southern areas (until 24°35″S) from those areas related to certain mountain ranges in the central Atlantic Rain Forest. The vicariant events were related to the uplifting of the Serra do Mar and the Serra da Mantiqueira, and the appearance of large rivers and climatic changes.