Studies on the optimum inclusion level of Ocimum gratissimum (scent leaf) to the diet of Clarias gariepinus post-fingerlings on its growth and development was studied 16wks using 15 out-door tarpaulin tanks of dimension 1m x 1m x 1m. Tanks were grouped into five (5) treatments in triplicates (T1a-c to T5a-c). Treatment T1a-c is the control. Three hundred (300) post-fingerlings of Clarias gariepinus used were randomly distributed in twenties into each of the tanks. Fishes in the tanks were fed 2.0mm coppens at 3% body weight two times daily. Treatments T2-T4 were respectively fed diets containing 10g ,20g,30g, 40g of ground O. gratissimum per Kg of feed. Treatment T1 had no O. gratissimum inclusion. Length and weight of fish samples were measured fortnightly and used as growth parameters. Data collected were subjected to one-way analysis of variance and means were separated using Duncans multiple range test. The result obtained revealed that an increase in the inclusion level of O. gratissimum, beyond 10g per Kg of feed results in a decline in growth rate of fish. Optimum fish survival rate was also obtained in treatment 2. It is therefore concluded that the optimum inclusive level of O. gratissimum to achieve maximum growth is 10g/kg of feed.