Background: An association between breast cancer and immune thrombocytopenic purpura (ITP) is very rare; there are only 18 cases reported in the English literature so far. Patients and Methods: A 65-year-old woman who had been diagnosed with ITP 5 years ago presented with 2 palpable masses in her left breast. Following establishment of the histopathologic diagnosis of invasive ductal carcinoma by fine needle aspiration biopsy, the patient underwent left modified radical mastectomy. Results: Histopathologic examination confirmed invasive ductal carcinoma in the bigger mass, and in situ ductal carcinoma in the smaller. The case was T2NoMo, therefore exclusive anti-estrogen therapy was started for the next 5 years. However, thrombocytopenia recurred twice in the first postoperative year. Fluorodeoxyglucose positron emission tomography (FDG-PET) scanning showed no breast cancer metastases anywhere in the body. Following immunoglobulin infusion, the platelet count increased enough for surgery, and the patient underwent splenectomy for ITP in the 10th month after the previous breast cancer surgery. After an uneventful postoperative period, the patient has been symptom-free during the 1-year of follow-up with normal platelet levels. Conclusion: Although the relevant current data are conflicting, in the present case no direct relationship between ITP and breast cancer could be observed clinically.