Local chest wall relapse following mastectomy for ductal carcinoma in situ (DCIS) is an unusual event. We report on 10 cases of patients treated with mastectomy for DCIS who subsequently experienced a chest wall relapse as the first site of recurrence. To our knowledge, this is the largest reported collection of postmastectomy chest wall relapses for DCIS. The tumor registry and medical records from Yale-New Haven Hospital of all patients treated for ductal carcinoma in situ were reviewed. Individual records and radiation therapy charts of those patients sustaining a chest wall relapse following mastectomy were reviewed in detail. All pathology from the original mastectomy, as well as from the chest wall relapse, was re-reviewed by the pathologist. All chest wall relapses were treated with radiation therapy, with or without adjuvant systemic therapy. Of the 10 cases, 9 patients remain alive without evidence of disease. Young patient age, multiquadrant disease, and the presence of residual normal breast tissue were common features among these chest wall relapses. Pathological features of the original mastectomies and chest wall relapses are presented and discussed. Postmastectomy chest wall relapses in patients with DCIS are an uncommon event. Patients treated aggressively with resection of the lesion followed by radiation therapy to the chest wall have a favorable prognosis.