The objective of the present study was to report the occurrence of Trypanoxyuris in owl monkeys, using data from clinical and haematological examinations, as well as clinical chemistry (blood urea nitrogen (BUN), creatinine, alanine aminotransferase (ALT) and aspartate aminotransferase (AST)) of infected and uninfected animals. Twenty animals in apparently good clinical health were studied. The coproparasitological examinations showed eggs compatible with Trypanoxyuris sp. in 50% of animals. The number of red blood cells, haematocrit and haemoglobin levels were significantly higher in the males, compared to the females, irrespective of parasitism. However, comparing segmented neutrophils in infected males and females, a significant difference (P < 0.05) was observed. All blood chemistry values were considered normal for the species pattern, even though significant differences were observed for BUN and ALT in infected males. The infection by Trypanoxyuris sp. did not appear to interfere with the clinical condition of animals.