The morphological characterization of ovaries and ovarian follicular oocytes obtained from the owl monkey is detailed in the present paper. In vitro maturation of oocytes, using a method which has proved successful for other mammalian oocytes, was also evaluated and the maturation rate was compared with that obtained with squirrel monkey oocytes. The ovaries of the owl monkey are oval in shape (long axis of about 10 mm, short axis about 7 mm) and their oocytes are spherical. The mean diameter of owl monkey oocytes is significantly larger than that of squirrel monkey oocytes (145.7 ± 16.3 µm vs 112.0 ± 12.4 µm). The owl monkey oocytes were incubated in HTF medium containing 10% FBS at 37 °C (5% CO₂ in air) for 22–23 hours. The in vitro maturation rate of the owl monkey oocytes was higher than that of the squirrel monkey oocytes (83.3% vs 40.0%); therefore, our maturation conditions were as suitable for them. This study is the first to detail differences in the follicular oocytes of the owl monkey and squirrel monkey. Further studies using owl monkey gametes might yield results leading to a greater understanding of primate reproduction.