BACKGROUND: Although acellular dermal matrix (ADM) is widely used in expander-implant-based breast reconstructions, previous analyses have been unable to demonstrate improvements in patient-reported outcomes (PROs) with this approach over non-ADM procedures. This study aims to develop a more selective, evidence-based approach to the use of ADM in expander-implant-based breast reconstruction by identifying patient subgroups in which ADM improved clinical outcomes and PROs. STUDY DESIGN: The Mastectomy Reconstruction Outcomes Consortium Study prospectively evaluated immediate expander-implant reconstructions at 11 centers from 2012 to 2015. Complications (any/overall and major), and PROs (satisfaction, physical, psychosocial, and sexual well-being) were assessed two years postoperatively using medical records and the BREAST-Q, respectively. Using mixed-models accounting for centers and with interaction terms, we analyzed for differential ADM effects across various clinical subgroups, including age, body mass index, radiation timing, and chemotherapy. RESULTS: Expander-implant-based breast reconstruction was performed in 1451 patients, 738 with and 713 without ADM. Major complication risk was higher in ADM users vs. nonusers (22.9% vs. 16.4% and p = 0.04). Major complication risk with ADM increased with higher BMI (BMI=30, OR=1.70; BMI=35, OR=2.29, interaction p = 0.02). No significant ADM effects were observed for breast satisfaction, psychosocial, sexual, and physical well-being within any subgroups. CONCLUSION: In immediate expander-implant-based breast reconstruction, ADM was associated with a greater risk of major complications, particularly in high-BMI patients. We were unable to identify patient subgroups where ADM was associated with significant improvements in PROs. Given these findings and the financial costs of ADM, a more critical approach to the use of ADM in expander-implant reconstruction may be warranted.