this experiment was carried out to investigate the effects of supplementing two macroalgae Sargassum cristaefolium and Gracilaria pygmaea extracts in feed on some growth indices, hematology and blood constituents of juvenile rainbow trout (Onchorhynchus mykiss). Rainbow trout were randomly divided into four groups: a control group was fed with basal diet, and three treated groups fed with basal diet supplemented with 500 (mg/kg) S.cristaefolium (SA), 500 (mg/kg) G.pygmaea (GL) and 250 (mg/kg) S.cristaefolium + 250 (mg/kg) G.pygmaea (SA+GL) for 8 weeks. The fish were fed 4 times by hand to apparent visual satiation and water was changed every day. Results showed that growth factor such as final fish weight, specific growth rate (SGR), weight gain (WG) and condition factor (CF) were not significantly different among treated groups (P > 0.05). Hepatosomatic index (HSI) was significantly higher in fish fed control or SA diets (P < 0.05). Among the blood parameters, hemoglobin levels in fish fed diet containing gracilaria was significantly higher than the control group (P < 0.05). Among the biochemical composition of blood, group fed the control diet had higher triglycerides level compared to the groups fed diets containing sargassum or a mix of sargassum and gracilaria (P < 0.05). These results indicated that dietary supplementation of sargassum and gracilaria extracts in rainbow trout feed had not significant impacts on growth performance and blood parameters of this fish.