The present study was carried out to investigate the effect of green algae Ulva lactuca and red algae Pterocladia capillacea at 0.0, 2.5 and 5% on growth performance, feed utilization, carcass composition and blood indices of Nile tilapia, Oreochromis niloticus fingerlings. Fish (18.47 ± 1.25 gm) were randomly divided into fifteen aquaria in triplicates and fed diets contained about 29.51% total protein and 4.53 kcal/g gross energy. All the growth performance parameters and feed utilization values of experimental fish were increased significantly (P ≤ 0.05) by both of algae supplementation. Diet supplemented with 5% of Ulva lactuca had acceptable growth parameters compared with other diets. Fish fed supplemented diets had slight increases and decreases for carcass protein and lipids without significant differences (P ≥ 0.05). Also, no significant differences (P>0.05) were obtained for serum total protein, albumin and globulin and liver activity. It may be summarized that, algae supplementation especially at 5% of Ulva lactuca level may improves growth parameters and carcass composition without adverse effects on blood metabolites and liver activity.