The digestibility of corn gluten meal (CGM) and possibility of its inclusion in tilapia dicts were studied in two steps. Firstly, CGM was fed as a sole dietary ingredient to tilapia and showed digestability coefficient (DC) of 86.32, 82.2 and 74.8 % for CP , EE ang GE, respectively. Secondly, an experimental study was done to investigate the effect of CGM inclusion rate (25, 50 and 100 %) in fish diets replacing either soy bean meal (SBM) or fish meal (FM) on tilapia performance. In addition, the DC of such diets was determined. Tilapia fed on diets contained CGM (especially at high inclusion rate) did not perform well as those fed on SBM-FM control diet. Although 25 % replacing level of SBM by CGM surpassed all dietary treatments in CP and EE digestibility. It can be concluded that, CGM can successfully replaces either SBM or FM in fish diets up to 25% of the total protein in case of their shortage.