A 12-week feeding trial was undertaken to evaluate the effect of dietary graded levels of a commercial probiotic, Biogen® (containing allicin, high unit hydrolytic enzyme, Bacillus subtilisspores and ginseng extract) on growth, survival, feed utilization, haematology parameters and proximate composition of Nile tilapia, Oreochromis niloticust. Five isonitrogenous (300 g CP kg dry matter, DM) and isocaloric (19.3 MJ gross 1 energy kg DM) diets were formulated and Biogen® was supplemented in five increased levels, 0, 1, 2, 3 and 1 4 g kg to formulate the five experimental diets, D1, D2, D3, D4 and D5, respectively. Fingerlings averaging 1 2.23±0.05g were randomly distributed into 15 glass aquaria (160 liter) and each aquarium holding 25 fish and randomly assigned to one of three replicates of the diets and offered feed to satiation to fingerlingsO. niloticus. Thecontrol diet exhibited lower growth and feed utilization than all Biogen® supplemented diets. The highest significant (P