The terminal ventricle is a dilation of the ventricular system located within the spinal cord, which is enveloped in ependymal cells that are involved in the dynamic of the cerebrospinal liquid. In the present study, four Saguinus leucopus specimens were dissected, two males and two females, whose spinal cords were extracted and histologically processed via hematoxylin and eosin stains of cuts at the conus medullaris. The S. leucopus’ terminal ventricle was observed at the conus medullaris, and had an average diameter of 241.38 μm. Thus, the presence of the terminal ventricle in the S. leucopus at the level of the conus medullaris was established.