This study was conducted to evaluate the effects of enzymes produced by five Bacillus probiotics on growth and nutritional parameters of rainbow trout (Oncorhynchus mykiss) larvae with an initial body weight of 0.53 ± 0.19 g during 60 days. The enzyme suspension produced by Bacillus probitics resulted from culturing the bacilli in broth media with three concentrations of 1×10⁶, 1×10⁷ and 1×10⁸ CFU/100g were inoculated into the diet of rainbow trout larvae. The results of larval biometry at the end of the period of the experiment showed the following: First, the use of enzyme suspension, produced by the highest concentration of Bacillus (1×10⁸ CFU/100g) fed in T3 treatments (20.02 ± 3.77 g), caused a significant increase in the weight growth (P<0.05). Second, the same results were observed in other growth parameters, such as specific growth rate and average daily growth. Third, the use of enzyme suspension caused a significant reduction in food conversion ratio in all experimental treatments (P<0.05). The result of nutritional parameters showed the improvement of protein, lipid, energy and fiber efficiency in experimental treatment compared with the control (P<0.05). Also, the retained protein and lipid were increased significantly in experimental treatments (P<0.05). Finally, the use of enzyme suspension in this study caused improved growth performance and feed utilization in rainbow trout larvae and also increased survival rate.