The research was performed at the Department of Animal Production's fish laboratory, National Research Center, Dokki, Egypt. The research was conducted to assess the impact of commercial powder probiotic (ZADO®) on growth efficiency of Nile tilapia mono-sex fish (O. niloticus), which were fed on basal experimental diet (the control group)and other 4 experimental diet, which was the basic diet augmented with 0.25,0.5,0.75 and 1% of ZADO® for T1, T2,T3,T4 andT5, respectively. The Five experimental treatments were performed in three replicates each, the experimental aquaria were part of closed recirculating system, where environmental parameters were kept constant throughout the experimental period. Fifteen aquaria 60 × 40 × 30 cm, width, depth, and height, respectively each was stocked with 15 fish. The mean individual initial body weight (4.04 g/fish) was recorded at the start of the experiment. All fish in each aquarium throughout the entire experimental period were weighed every two weeks. The experimental fish were fed 32 % crude proteinbased diet for (98 days). The daily feed allowances were calculated as 5% of fish body weight and were divided into 3 portions fed at 8 am, 12 pm and 4 pm. The Results of the experiment indicated that T2 had the largest significant (P<0.05) final body weight (FBW g/fish), average weight gain (AWG, g/fish), specific growth rate (SGR % day), feed conversion ratio (FCR), feed efficiency ratio (FER) and protein efficiency ratio (PER) among all the experimental groups. In addition, no substantial variations (p > 0.05) were found in protein productive value (PPV). Although significant effects (p <0.05) have been reported in fish body crud protein (CP) and fat (EE) in T2. By increasing ZADO levels in experimental diets higher than 0)25% no significant effect were observed.