A 36-yr-old male captive siamang (Symphalangus syndactylus) was evaluated for mange in the form of generalized alopecia, flaky skin, and pruritus of 1 mo duration. Multiple skin scrapings and biopsies revealed high numbers of trombidiiform mites identified as Psorobia (formerly Psorergates) sp. near cercopitheci (Acarina: Psorergatidae) based on morphologic characteristics. Prolonged repetitive treatment with ivermectin killed the mites and resolved the clinical signs. Psorergatid mites should be considered as a cause of dry flaky skin in even long-term captive siamangs or other primates. This is the first record of psorergatid mites from a primate host in the family Hylobatidae.