Ascorbic acid (C) is needed for fish physiological functioning and growth. A feeding trial of 60 days was conducted to determine the optimal rational C inclusion level for the red tilapia juveniles based on growth, serum biochemical markers, antioxidative capacity, and ovarian fatty acid profile. Four diets were designed to have graded C concentrations of 0, 0.1, 0.2, and 0.3g/ kg diet (C0, C1, C2, & C3). The experimental period was followed by an additional 60 days to assess the spawning efficiency of the experimental fish groups. The results revealed that C did not improve the indicators of fish development performance or biochemical composition but did increase serum antioxidant activity. Furthermore, fish immunity was improved.  The gonadosomatic index, hepatosomatic index, and relative fecundity were significantly increased with higher percentages of C, which also led to an increase in ovarian EPA and DHA contents. An increase in spawning efficiency was associated with increasing the C supplementation level based on the spawns' number for each female, the mean eggs number per spawn, and decreasing inter-spawn intervals. The statistical analysis revealed that the ideal C level in the diet was 0.3g/ kg for improving fish immunity, reducing oxidative stress, optimizing reproductive parameters for supporting the production of good egg and larval quality for the red tilapia broodstock profitability.