Competing hypotheses exist concerning the influence of ranging patterns on parasitism. More intensive use of a home range could result in greater exposure to infectious agents that accumulate in the soil. Alternatively, when more intensive ranging is associated with territorial defence, this could decrease home range overlap and produce lower levels of parasitism. We tested these hypotheses using phylogenetic comparative methods and parasite richness data for 119 primate species. Helminth richness increased with the defensibility index, a quantitative measure of home range use that correlates with the degree of territoriality in primates. This association was independent of other host traits that influence parasite richness in primates. Results involving non-vector transmitted helminths produced the most significant results, suggesting that the relationship between territorial behaviour and parasitism is driven by accumulation of parasites in defended home ranges. In addition, costs associated with greater ranging could increase susceptibility to infectious agents.