BACKGROUND: Herbal immunostimulants have numerous potential benefits in comparison to vaccines and drugs like antibiotics in aquaculture. OBJECTIVES: In this study, effects of administration of Echinacea purpurea in oral and intra peritoneal routs on some hematological and immunological parameters of the grass carp (Ctenopharyngodon idella) were investigated. METHODS: A total of 240 healthy juvenile grass carp were randomly divided into four equal groups in triplicates. Group 1 received 400 mg/kg b.w. Echinacea in intra peritoneal injection. Group 2  received 0.5% Echinacea in their daily food. Group 3 and 4 were considered as injection control and oral control, respectively. Fish were bled on day 0, 10, 20, 30 and 40 of study. Sera samples were assayed for immunological parameters: lysozyme activity, serum bactericidal activity, complement activity and NBT reduction assay. Blood samples were also used for hematological parameters: (PCV, Hb, RBC, WBC and Leukocyte differentiated count). RESULTS: Results showed that serum lysozyme and bactericidal activity as well as complement and NBT reduction activity were significantly higher in i.p. treatment than the control group (p<0.05), while in oral treatment bactericidal and NBT reduction activity increased significantly on days 30 and 40 (p<0.05). Hematological assay shows no significant differences in PCV, Hb and RBC values at each sampling period in oral and injection compared to controls (p>0.05) but WBC count and  rate of heterophils showed an increase in injection treatment group compared with the control (p<0.05). Mortality rate after challenged with A. hydrophila decreased in Echinacea treated treatments. CONCLUSIONS: This study indicates that administration of E. purperea stimulates some nonspecific immune responses in grass carp and therefore it can be recommended as an herbal immunostimulant in fish.