Apart from its use for protection, temperature regulation, and identification of species, mammalian hair can be used in forensic biology through morphological analysis to identify trafficked endangered wildlife. This study determined the morphological characteristic of dorsal guard hairs of four species of Cercopithecidae family obtained from hunters in Omo Forest Reserve, Ogun State, Nigeria. These were mona monkey (Cercopithecus mona), putty-nosed monkey (Cercopithecus nictitans), red-capped mangabey (Cercocebus torquatus), and white-throated monkey (Cercopithecus erythrogaster). Data on qualitative and quantitative morphological characteristics of hair samples were obtained and analysed using standard methods. The qualitative features determined were scale patterns and medulla type; while the quantitative were scale length and width, shaft diametre (μm), medulla diametre and medulla index and fraction. C. mona had the highest values in shaft (387.00±75.38) and medullary (226.00±59.73) diametres, scale length (218.76±60.29) and width (725.76±155.91), and medullary index (0.58±0.13) and fraction (58.4±12.60). All the quantitative hair morphologies of the four species were significantly different (P≤0.05) except scale length (which was significant at P≤0.07). A post hoc test showed that the medullar diametre of C. mona was significantly different (P≤.003) from the other species. The medullary diametre of C. nictitans was significantly different (P≤0.05) from C. torquatus. The medullary index of C. mona was significantly different from that of C. nictitans (P≤0.017), C. torquatus (P≤0.001), and C. erythrogaster (P≤0.003). The differences observed in the morphological features of the sampled hairs could be used in species identification and a database for any trafficked member of these four species from Nigeria.