The purpose of this study was to evaluate the effect of two fermented fruit wastes (FFW) as feed additives on the growth rate, economic analysis, intestinal microbiota, digestive enzymes, and gene expression in the postlarvae (PL) of Litopenaeus vannamei. Three diets (38% crude protein, 9% crude lipid) consisting of T₀ (control), T₁ (2.5% fermented grape bagasse) and T₂ (2.5% fermented banana peels) were devised and given to the shrimp PL (n = 80 PL/tank in triplicate) for 45 days. The findings showed that adding dietary FFW supplements to shrimp diets significantly improved their survival rate (S%), final body weight (FBW), weight gain (WG) and specific growth rate (SGR). The feed conversion ratio (FCR) was also reduced by the FFW. There was an increase in the total bacterial count (TBC) in water and shrimp intestines, while total vibrio count (TVC) was reduced by the FFW. The addition of FFW could considerably enhance the activities of the investigated enzymes in the intestine, hepatopancreas and stomach, especially in T₂ followed by T₁ (P< 0.05). Furthermore, the levels of all studied genes in the shrimp's hepatopancreas given fermented banana peels were considerably greater (P< 0.05) than those of the control group. The results indicated that the shrimp fed with fermented banana peels presented the highest growth rate, better digestibility, and growth-related and immune-related genes. In conclusion, FFW can be used in modest amounts as immunostimulants in shrimp diets to promote the growth and health of shrimp.