A feeding trial was conducted to study the possibility of replacing the fish meal (FM) with fermented fish by-product silage (FBS) as non-conventional ingredients in the diets of the Nile tilapia, Oreochromis niloticus fingerlings. Five isonitrogenous (300 g CP kg^-1 dry matter, DM) and isocaloric (19 MJ gross energy kg^-1 DM) diets were formulated and FM was replaced by FBS in five increased levels, 0, 25, 50, 75 and 100% g to formulate the five experimental diets, FBS0, FBS25, FBS50, FBS75 and FBS100, respectively. Three hundred O. niloticus fingerlings (18.53±0.70g) were randomly distributed into 15 glass aquaria (160 liter), and were divided into five groups (three aquaria for each group) and each aquarium holding 20 fish. Experimental fish were fed onon the formulated diets for 84 days. Replacing of FM with FBS up to 25% did not significantly (P<0.05) affected growth and feed utilization parameters, while the other substitution levels (50,75 or 100%) significantly (P<0.05) reduced growth and feed utilization parameters. Fish offered the control diet exhibited the highest significance (P<0.05) average body weight (BW), body length (BL), weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER). Fish group fed onon FBS25 gained the highest significant protein content and the lowest fat and ash content of carcasses compared to the control and the other fish groups Generally, replacing 25% of FM by FBS did not significantly affected growth and feed utilization parameters and reduced feed costs by 7.93% for tilapia fingerlings.