This study was designed to evaluate the effects of oral administration of Echinacea hydroethanolic extract on the dog's immune system. The study was performed on 14 dogs that were referred to the veterinary clinic. These dogs were randomly allocated to two equal treatment groups. The first group received 1 ml of 5% Echinacea hydroethanolic extract two times a day for 2 months, and the second group received a placebo (water). To do haematology and immunology tests, the dogs were bled on days 0, 30 and 60. Blood tests, including packed cell volume (PCV), haemoglobin (Hb), red blood cell count (RBC), white blood cell count (WBC), counting neutrophils (Nut), lymphocytes (Lym), monocytes (Mon), eosinophils (Eos), basophils (Baso) and B cell, were performed. Furthermore, safety factor IgM and per cent of phagocytosis and phagocyte were measured from the blood sample. The results showed that in the group which received Echinacea PCV, Hb, RBC count, WBC count, Lym, Nut, the per cent of phagocytosis and IgM significantly increased (P < 0.05). Moreover, positive effects of Echinacea plant on the immune system were observed. There was a significant change in HTC, RBC, Hb over time in the group that received Echinacea and the per cent of phagocytosis and IgM (P < 0.05). The study establishes that these extracts might have appreciable immunostimulatory activity. However, further studies are required to confirm these findings.