The pre-mastectomy sentinel lymph node biopsy (PM-SLNB) is a technique that provides knowledge regarding nodal status prior to mastectomy. Because radiation exposure is associated with poor outcomes in breast reconstruction and reconstructed breasts can interfere with the planning and delivery of radiation therapy (RT), information regarding nodal status has important implications for patients who desire immediate breast reconstruction. This study explores the safety and utility of PM-SLNB as part of the treatment strategy for breast cancer patients desiring immediate reconstruction. We reviewed the charts of adult patients (≥18 years old) who underwent PM-SLNB from January 2004 to January 2011 at our institution. PM-SLNB was offered to patients with stage I or IIa, clinically and/or radiographically node-negative breast cancer who desired immediate breast reconstruction following mastectomy. PM-SLNB was also offered to patients with ductal carcinoma in situ if features concerning for invasive carcinoma were present. Ninety-one patients underwent PM-SLNB of 94 axillae. PM-SLNB was positive in 25.5% of breasts (n= 24). Nineteen node-positive patients (79.2%) have undergone or planning to undergo delayed reconstruction at our institution. Seventeen of these 19 node-positive patients (89.5%) have received adjuvant RT. Two patients (10.5%) elected against RT despite our recommendation for it. No biopsy-positive patient underwent immediate reconstruction or suffered a radiation-induced complication with their breast reconstruction. There were two minor complications associated with PM-SLNB, both in node-negative patients. This study demonstrates the utility of PM-SLNB in providing information regarding nodal status, and therefore the need for adjuvant RT, prior to mastectomy. This knowledge can be used to appropriately counsel patients regarding optimal timing of breast reconstruction.