Purpose: Two-stage tissue expander (TE) to implant breast reconstruction is commonly performed by plastic surgeons. Prepectoral implant placement with acellular dermal matrix (ADM, e.g., AlloDerm®) reinforcement is evidenced by minimal postoperative pain. However, the same is not known for TE-based reconstruction. We performed this study to explore the use of complete AlloDerm® reinforcement of breast pocket tissues in women undergoing unilateral or bilateral mastectomies followed by immediate, two-stage tissue expansion in the prepectoral plane.Methods: Patients (n = 20) aged 18-75 years were followed prospectively from their preoperative consult to 60 days post-TE insertion. The pain visual analog scale (VAS), Patient Pain Assessment Questionnaire, Subjective Pain Survey, Brief Pain Inventory-Short Form (BPI-SF), postoperative nausea and vomiting (PONV) survey, BREAST-Q Reconstruction Module, and short-form 36 (SF-36) questionnaires were administered. Demographic, intraoperative, and 30-and 60-day complications data were abstracted from medical records. After TE-to-implant exchange, patients were followed until 60 days postoperatively to assess for complications.Results: Pain VAS and BPI-SF pain interference scores returned to preoperative values by 30 days post-TE insertion. Static and moving pain scores from the Patient Pain Assessment Questionnaire returned to preoperative baseline values by day 60. The mean subjective pain score was 3.0 (0.5 standard deviation) with seven patients scoring outside the standard deviation; none of these seven patients had a history of anxiety or depression. Median PONV scores remained at 0 from postoperative day 0 to day 7. Patient-reported opioid use dropped from 89.5% to 10.5% by postoperative day 30. BREAST-Q: Sexual well-being scores significantly increased from preoperative baseline to day 60 post-TE insertion. Changes in SF-36 physical functioning, physician limitations, emotional well-being, social functioning, and pain scores were significantly different from preoperative baseline to day 60 post-TE insertion. Five participants had complications within 60 days post-TE insertion. One participant experienced a complication within 60 days after TE-to-implant exchange.Conclusions: We describe pain scores, opioid usage, patient-reported outcomes data, and complication profiles of 20 consecutive patients undergoing mastectomy followed by immediate, two-stage tissue expansion in the prepectoral plane. We hope this study serves as a baseline for future research.