In this study, the effect of fish meal substitution with fermented soybean meal in juvenile tilapia (Oreochromis niloticus, L. 1758) diets was investigated. Six experimental diets were prepared by replacing 0 (FM, control), 10% (FSM10), 20% (FSM20), 30% (FSM30), 40% (FSM40), and 50% (FSM50) of the fish meal protein in the control diet by fermented soybean meal with whey (FSMW). The control diet contained no fermented soybean meal. The isonitrogenous and isocaloric diets were fed to juvenile tilapia (initial average weight 0.74 g) for 90 days. Each diet group was fed in triplicate to 24 fish per aquarium. At the end of the experiment, highest growth, feed efficiency, and protein digestibility were found in the group fed the FSM30 diet. Tilapia fed diets containing fermented soybean meal up to 50% fish meal exhibited similar growth, feed conversion ratio (FCR), protein efficiency ratio (PER), and protein digestibility compared with the control diet. However, feed efficiency (FE) was reduced in tilapia fed FSM50 diet. Body composition, hepatosomatic index (HIS) and viscerosomatic index (VSI) were unaffected by the dietary treatment. Results of this study showed that FSMW could replace up to 40% of fish meal protein in juvenile tilapia diets.