Granulomatous amoebic encephalitis caused by the free-living amoeba Balamuthia mandrillaris is a highly fatal disease that was first isolated from a mandrill (Mandrillus sphinx), and has since been diagnosed in several nonhuman primates including orangutans. Indirect immunofluorescence antibody (IFA) techniques for Balamuthia have been used in the fields of human medicine and epidemiology both for exposure assessment and screening of clinical patients for antemortem diagnosis. Stored serum samples from five captive Northwest Bornean orangutans (Pongo pygmaeus pygmaeus), including one who had died from B. mandrillaris infection, housed at a single facility were screened with a human IFA assay for B. mandrillaris. Only the single, clinically affected individual was seropositive, and the results suggest that the use of the available human B. mandrillaris IFA assay is a novel diagnostic option for detection of Balamuthia antibodies in this species. A validated screening serological test could be used in individuals exhibiting signs consistent with granulomatous amoebic encephalitis to facilitate earlier antemortem diagnosis of Balamuthia infection, which is critical if treatment is to be pursued. This pilot study presents the use of serological detection methods for B. mandrillaris screening in a nonhuman primate. Subsequent use of the B. mandrillaris IFA assay in the larger captive population should be pursued for validation of the test and to provide further information on seroprevalence and evaluation of risk factors for exposure to Balamuthia and subsequent development of disease.