In this study, we partially replaced fishmeal (FM) with moringa protein hydrolysate (MPH) in the diet of Nile tilapia, Oreochromis niloticus, in a ten-week feeding trial. We evaluated the consequences of this substitution on the growth, digestive enzyme activity, economic efficiency, immune status, and expression of immune genes, protein transporters, and insulin growth factor-1 (IGF-1). Fish (n = 225, 36.38 ± 0.06 g/fish) were randomly assigned to five groups with five replacement levels of MPH: 0, 15, 30, 45, and 60% (MPH0, MPH15, MPH30, MPH45, and MPH60). The results showed a linear increase in the growth parameters by replacing FM with MPH. A rise in the serum level of growth hormone and a reduction in the leptin hormone and glucose levels were observed with increasing the MPH replacement level. Higher amylase activity was detected with MPH replacement, with the highest activity noticed in the MPH45 group. The protease activity was linearly increased in the MPH45–60 groups. We reported significant up-regulation in the expression of IGF-1 and amino acid and peptide transporters in MPH groups. The immune indices (serum nitric oxide level, lysozyme activity, and phagocytic activity) and immune-related gene expression were linearly up-regulated by MPH replacement up to the 45% replacement level then decreased in the MPH60 group but still higher than the control group. FM replacement with MPH increased the Nile tilapia resistance to Aeromonas sobria challenge. In conclusion, MPH can replace FM up to 60% for good performance and immune status of fish.