The morphology, sizes and abnormality rates of spermatozoa in the night monkey were revealed in the present paper. Motile spermatozoa of three males, 7, 8 and 12–13 years old, were squeezed from the ducts of the cauda epididymis after cutting the ducts in cryopreservation media. The morphology of the spermatozoa and abnormalities in them were observed, and the sizes of the spermatozoa were measured in smear samples. The spermatozoa of the night monkey had heads with rounded and thick shapes. Measurement of the spermatozoa revealed that the average widths and lengths of the heads, average lengths of the middle pieces, and average total lengths from the head to tail tip were 4.7 ± 0.8, µm and 2.8 ± 0.4 µm, 6.6 ± 2.2, µm and 55.1 ± 6.2 µm, respectively (average ± SD). The total rates of abnormal spermatozoa were different among the 7-, 8- and 12–13- year-old night monkeys, 41.8%, 24.0% and 36.5%, respectively. Freezing of semen was also attempted using the procedure contained in a commercial kit for the mouse. Although the motility of the spermatozoa from the night monkeys was poor in fresh samples, the motility of their spermatozoa frozen-thawed with the commercial kit was similar to that before freezing.