and its effect on the histology of testis ovary and liver was assessed. Using 150 juveniles of Oreochromis niloticus, the sterility effect of Petiveria alliacea root bark meal (PARBM) was determined in a 56-day feeding experiments at the inclusion levels of 0g, 15g, 20g, 25g and 30g / kg diet. Each of the treatments were in three replicates and the fish were fed at 4% body weight twice daily. Behavioral responses of fish and physiochemical parameters of water were monitored during the experiment. The results showed that the testis weight was not significantly different. Milt counts and milt volume reduced with increase in the concentration of Petiveria alliacea root bark meal. Motility duration also decreased with increase in the inclusion levels. Also, the fish exhibited significant differences (P<0.05) in the final weight of 0g and 20g / kg PARBM level. Ovary weight reduced with increase in the concentration of PARBM. The histology of the testes of fish fed 0g of PARBM/kg diet revealed that primary and secondary spermatocytes were present in seminiferous tubule, while in treatment 15g, 20g, 25g, and 30g of PARBM/kg diet, secondary spermatogonia was seen in the lumen of the seminiferous tubule. Section of testis exposed to 20g showed increase in interstitial cell and necrosis, 25g showed gonadal degeneration and necrosis while section exposed to 30g showed spermatids disintegration and necrosis. Developing oocytes surrounded by a thin wall were observed in the histological examination of the ovary of O. niloticus fed 0g of PARBM/kg diet; 15g showed section of ovary filled with developing oocytes, 20g showed developing oocytes and some necrotic oocytes, 25g showed deteriorating oocyte and interstitial cell alteration in ovary development and 30g showed no oocytes in the lumen and alteration in ovary development. Histological observation and gonadal analysis revealed that Petiveria alliacea root bark meal can be used as sterility agent in Oreochromis niloticus under culture conditions.