An evaluation of using crayfish as partial or complete replacement of fish meal protein in Nile tilapia fry was conducted .The obtained results showed that, the best feed conversion was noticed in control group, which fed on fish meal (FM) without any replacements, followed by group II which treated with crayfish meal (TCFM) 50%, then group IV, which received treated crayfish meal (100%), then group I where the worst value of feed conversion was noticed in diet containing crayfish by-product (CFBM) 50% replacement. Body composition showed no significant difference between different experimental diets and the control one, except with (TCFM) 100% diet. Results of heavy metals analysis showed that fish of group II had the lowest concentrations of Cu, Cd, Pb, Fe and Zn than that in group I (CFM) and III (CFBM). On the other hand, it was noticed that the estimated levels of both cadmium and lead in fish of group II (TCFM) were lower than that of control group.