We report a case of isolated local recurrence of breast cancer, which was accompanied by idiopathic thrombocytopenic purpura (ITP) and benign monoclonal gammopathy that presented 24 years after the patient underwent mastectomy. A 72-year-old female patient with a chest wall tumor was referred to our hospital in November 1994. Twenty-four years previously she had surgically treated breast cancer, of which the pathology was scirrhous carcinoma. Needle biopsy of the tumor revealed tubular carcinoma, which is compatible with local recurrence of breast cancer. She had no evidence of regional lymph node involvement or distant metastasis. Hematological and serological examination revealed a low platelet count accompanied by M-proteinemia (IgG, kappa-type) and a mild increase in platelet-associated IgG. She was initially treated with extensive-field chest wall radiation (60 Gy), followed by systemic administration of tamoxifen. Complete local control of isolated local recurrence (LR) was achieved after radiation therapy (RT) and the patient has been progression-free for more than 2 years. Platelet count recovered gradually to a normal level after achievement of complete remission induced by radiation and tamoxifen. This may be the first case suggestive of a paraneoplastic syndrome of immune thrombocytopenia accompanied by local recurrence of breast cancer.