The aim of this report was to determine the frequency of thrombocytopenia in a cohort of 1,126 patients receiving oral anticoagulant therapy (OAT), and to compare the grade of thrombocytopenia and the severity of bleeding complications. Severe thrombocytopenia was observed in five patients, and moderate and light thrombocytopenia were observed in 208 patients. Thrombocytopenic patients receiving OAT presented five major and six minor hemorrhages. The presence of hepatitis markers and autoantibodies was assessed. All parameters at the time of the bleeding complication were in the therapeutic range.