This study was designed in order to determine the effect of changing stocking density on individual growth of rainbow trout (Oncorhynchus mykiss) during a 60-day period. Fish (average weight: 30 gr) were cultured in triplicates of fiberglass tanks under stocking density 0f 14, 22, and 29 fish/m² as T1, T2 and T3 respectively. In the 30^th day, juveniles from lower density tanks were moved to higher density tanks and vice versa. On the 30^th day, significant difference was detected on body weight among treatments (P<0.05). Also, result showed significant differences in body weight index, specific growth rate, net final production, final weight and FCR among the treatments (P<0.05). On the contrary, significant difference in effect of density on body weight index, body weight gain, net final production, final weight and FCR seemed to be within reach between the treatments after moving the fish to different densities (P<0.05). Results of hematological analysis showed significant decrease in T3 for values of WBCs count. Values of RBC, Hb, PSV, MCV, MCH, and MCHC showed non-significant differences among treatments. Changing the stocking density had non-significant effect on values of WBC, PSV, MCV, MCH and MCHC, while values RBC and Hb showed significant differences among treatments. In conclusion, the slow growth caused by high density can be compensated by rearing the fish in low density.