The aim of the present study was to investigate the effect of chitosan nanoparticles (CsNPs) synthesis using Spirulina platensis for European seabass (D. labrax) on the growth performance, blood hematological and biochemical parameters. Therefore, Six experimental diets were formulated to provide 45% crude protein and 499k cal./100 g diet and supplemented by S. platensis and chitosan as following: T1: control, T2: 0.05% S. platensis, T3: 0.1% S. platensis, T4: 1 ml chitosan, T5: 1 ml chitosan and 0.05% S. platensis, T6: 1 ml chitosan and 0.1% S. platensis. Each diet was offered twice daily at 5% feeding rate in two replicate fish groups (22.6-22.9 g/fish) stocked at 15 fingerlings per m³ for each of 12 (1×2.5×1m³) hapas for 16 weeks. Diet supplementation by each of spirulina and chitosan nanoparticles (T5 and T6) significantly improved (P<0.05) growth performance and survival rate values compared to the control group. Fish fed diets T5 and T6 showed the highest blood hematological and biochemical parameters compared to the control treatment (P<0.05). The results suggested that that diet supplementation by spirulina and chitosan nanoparticles improves the growth performance, blood hematological and biochemical parameters of the European seabass (Dicentrarchus labrax).