The present study was conducted to investigate the effects of Genesis (G, a commercial mixture of phytoestrogens) oil growth, body composition and sex differentiation of Sharptooth catfish Clarias gariepinus. Genesis is a commercially available product on USA and European markets used for menopausal complaints as an alternative medicine. Different concentrations (0 mg G 30 L(-1), 210 mg G 30 L(-1), 420 mg G 30 L(-1), 630 mg G 30 L(-1), 750 mg G 30 L(-1) and 1500 mg G 30 L(-1)) of Genesis were administered by immersion of newly hatched larvae (averaging 2.27+/-0.12 mg) every 3 days for 30 days then immersion treatments were ceased and all groups reared in the same condition for the later 90 days, a total 120 days experimental period. At the end of the trial, specific growth rate of the females increased with the increasing concentration of Genesis up to 420 mg 30 L(-1) (P<0.05), but different concentrations of Genesis did not affect the growth performance of males (P>0.05). The highest value of protein content (21.60%) was observed from the 420 mg G 30 L(-1) group and found significantly different front the control and other groups (P<0.05). Also, lipid contents were significantly affected by the Genesis concentrations and the highest lipid contents were detected in the 210 mg G 30 L(-1) (5.98%) and the 630 mg G 30 L(-1) (6.66%) groups. Although among the dosages used in the present study, 1500 mg G 30 L(-1) was the most effective dosage that ensured maximum female ratio (69.77%), the sex ratios observed for 0, 210, and 420 mg G 30 L(-1) treatment groups were nearly the expected ratio of 1: 1 (male: female). Therefore, it was concluded that usage of higher doses and treatment durations of Genesis could be more effective for all-female production of the Sharptooth catfish population.