Tramadol abuse is a major health problem. Its effects on hemostasis showed controversial findings. The aim of the present study was to investigate the subchronic toxic effects of tramadol on some hemostatic parameters in Wistar albino rats. Before performance of the study, bleeding time, prothrombin time (PT), activated partial thromboplastin time (APTT) as well as Adenosine Diphosphate (ADP) induced platelet aggregation percentage were measured to get reference values for normal levels. Rats were then given tramadol by gavage in a dose of 20 mg/kg once daily for six weeks and the previously mentioned haematological parameters were measured at two, four and six weeks. The results reveal that tramadol enhanced bleeding tendency along the six weeks of the study as evidenced by prolonged bleeding time, PT, APTT, and decreased ADPinduced platelet aggregation. It can be concluded that tramadol could affect hemostatic parameters in favour of bleeding tendency. Further studies are warranted to confirm these effects and to investigate the possible underlying mechanisms and the potential reversibility of toxicity after drug abstinence.