A survey was conducted to determine the prevalence and seasonal abundance of egg, larval, and adult stages of helminths; oocyts of protozoans; and ectoparasites of plateau pikas (Ochotona curzoniae) in seven areas of southeastern Qinghai Province, China, during August 2006 and May 2007. Fecal samples collected from 430 plateau pikas were examined by the modified McMaster technique, which revealed that 83% of the samples contained eggs from two or more helminth species. Mean fecal egg counts were generally moderate and showed the same trend irrespective of the age or sex of the pikas. The prevalence and counts of cestode eggs showed strong seasonal relationships that corresponded with the rainfall pattern in the study area during the study period. Of the 430 plateau pika examined at necropsy, 89% contained adult nematode or cestode species, but none of these contained adult trematode species or protozoans. Overall, six genera of adult nematodes including Oesophagostomum sp., Cephaluris coloradensis, Eugenuris schumakowiescsi, Haemonchus sp., Trichuris sp., and Chbertiinae sp.; three genera of adult cestodes including Schizorchis sp., Ochotonae sp., and Hymenolepis nana; three ectoparasite species including Hypoderma curzonial, Pulex sp., and Ixodes ovatus; and one proscolex stage of a cestode, Echinococcus multilocularis or Echinococcus shiquicus, were encountered during the study. Other genera examined occurred in low numbers, which did not allow any meaningful comparisons. Overall, results suggest that four parasite species, Hypoderma curzonial, Pulex sp., Ixodes ovatus Neumann, and Cephaluris coloradensis, may be regulating factors in controlling future numbers of plateau pika in this study area. These data provide evidence of a natural biologic control mechanism of plateau pika on grassland habitats, and may be of use for identifying the mechanism of transmission of parasites between plateau pika, livestock, and humans.