A 12 week feeding trial was conducted with rainbow trout Oncorhynchus mykiss, fry (3.98 +/- 0.05 g, average initial weight) to determine the effects of supplemental exogenous enzymes on growth, digestibility, and body composition. Five diets were prepared adding pectinase, xylanase, cellulase enzymes, and a commercial enzyme complex, to diets containing 40% soybean meal. The experiment was conducted in triplicate in 15 tanks, each stocked with 45 juvenile fish. The results showed that addition of enzymes to diet containing 40% soybean meal had no significant effect on growth performance and feed conversion ratio. No significant differences were observed in the apparent lipid digestibility, apparent protein digestibility, and whole body composition among dietary treatments (P>0.05). In conclusion, the use of single or multi-components of commercial enzymes (tested in this case) are not sufficient to degrade the high levels of non-starch polysaccharides introduced into digestive tract by the diets containing soybean meal at the rate of 40%.