This study was performed to determine the effects of Evening primrose oil (EPO) on haemostatic parameters following 30 and 60 days administration of 90 mg/kg (EPO) to healthy male rabbits. The laboratory resulting in significant increase in Prothrombin time (PT), activated partial thromboplastin time (aPTT) assays (p<0.01), platelets count significantly decreased (p<0.01) at both times. While fibrinogen concentration are insignificantly decreased. These effects might be due to inactivation or inhibition of factors affecting coagulation.