In the present study, it was aimed to determine the effects of diet containing two seaweed species, Ulva lactuca and Enteromorpha linza, on the growth performance, feed utilization and body composition of rainbow trout. Two experimental diets were formulated with the usage of 10% U. lactuca meal and 10% E. linza meal in feed and control group had no seaweed ingredients. Each experiment was triplicate and each group had fourteen fish specimens with an average weight of 32.96 +/- 0.29 g. Fish were hand fed three times per day for 60 days. Significant differences were determined in weight gain, specific growth rate, relative growth rate and feed utilization between experimental and control groups ( P<0.05). Fish fed with the diet containing 10% E. linza meal had the poorest feed utilization. The survival rate ranged from 96% to 98% in all groups during trial period. Apparent net protein retention, protein efficiency rate, daily dry feed intake and total feed intake were significantly lower in fish groups which fed with the diet containing U. lactuca and E. linza than control group (P<0.05). The final levels of crude protein, crude lipid and crude ash were in higher rates in the body composition all the groups compared when compared to the initial level (P<0.05). The results of the experiment revealed that a diet with U. lactuca and E. linza inclusion at 10% levels resulted in a poorer growth and feed utilization for rainbow trout when compared to those of control group. Hence, more defined experiments seem to be necessary in order to determine the optimum dietary inclusion level of these seaweeds in rainbow trout diets.