In this study, four groups of Nile tilapia (O.niloticus) were fed diets in which chitin substituted cellulose (present in basal diet) by 0, 2%, 5%, and 10%. Another 4 groups were fed the same diets with the addition of 1g probiotic / kg diet. The group fed 10 % chitin + probiotic had the best growth performance parameters and feed conversion ratio (FCR). Condition factor (K) was optimal for the fish fed the highest chitin concentration with probiotic in addition to the control group. The group fed 10% chitin+probiotic exhibited a significant increase in the final weight, weight gain, and weight gain % over 0, 2, 10% chitin, and 0% chitin+probiotic groups. The control and the group fed 10% chitin with probiotic have the highest K. They have significantly increased K values over 2%, 5% chitin groups and the probiotic groups (0, 2, 5% chitin + probiotic). Aspartate aminotransferase and alanine aminotransferase activities in fish homogenate were not significantly changed between all groups. Catalase (CAT)  activity was increased significantly in 5% chitin+probiotic group overall groups. The group fed 10% chitin with probiotic has the lowest catalase which was non significantly changed in most groups. Also, Glutathione was increased significantly in the groups fed 2% chitin+probiotic and 10% chitin+probiotic over those of the control and 5% chitin. It was increased significantly in the groups fed the basal diet either supplemented with probiotics or supplemented with 5% chitin + probiotic over the control. Similarly, the total protein was significantly increased in 10% chitin group over all other groups. Its content in the control, 2% chitin and 5% chitin groups were significantly increased overall groups fed probiotic diet.  Therefore, and based on the presented data, worthy to recommend the use of chitin as an aquafeed additive in aquaculture.