In this study, the effect of 17b- estradiol on haematological indices in juvenile stellate sturgeon (Acipenserstellatus) was investigated. For this, 120 juvenile stellate sturgeons with an average weight of 40.9±1.1 g were divided to 2 treatments (20 fish/tank). Juvenile stellate sturgeon, Acipenserstellatus were intraperitoneally injected with estradiol-17b (E2; 0 and 5 mg/kg fish). The duration of the experiment was considered for 7 months and at the end of the experiment, 5 fish were randomly sampled for measuring haematological indices including number of red blood cells (RBC), white blood cells (WBC), hemoglobin (Hb), hematocrit (Hct), mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC). Results showed that hematological features of E2-treated fish showed significant reduction in number of red blood cells, haemoglobin concentration, hematocrit value and mean corpuscular haemoglobin (P<0.05), but no significant changes were observed in number of white blood cells, mean corpuscular volume and mean corpuscular haemoglobin concentration (P>0.05). These results revealed that the injection of E2 could cause anaemia in stellate sturgeon.