We report a case of chronic hepatitis C complicated with idiopathic thrombocytopenic purpura (ITP), successfully treated with interferon (IFN) beta. A 65-year-old woman was admitted to our hospital for the treatment of chronic hepatitis C with IFN beta. ITP was also diagnosed because of the presence of platelet associated IgG and the findings of bone marrow examination. We started IFN therapy, which resulted in normalization of transaminases, complete HCV eradication, and increased number of platelet.