A 6-yr-old male pale-headed saki monkey (Pithecia pithecia), born at the Dallas Zoo, reentered the collection in 1994 after it was housed for 4 yr in Rhode Island and 2 yr in Florida. The monkey tested negative for both Dirofilaria immitis microfilariae and D. immitis adult antigens (via commercially available tests) upon return. However, it tested positive for adult antigens 1 yr later, and additional testing, including ultrasonography, suggested a diagnosis of aberrant dirofilariasis. Relevant evidence of previous microfilaremia in pale-headed saki monkeys at the Dallas Zoo is reviewed. Dirofilaria immitis infection should be included in the differential diagnosis list for any nonhuman primate with cardiopulmonary disease wherever the parasite is enzootic.