Background:Few studies have assessed long-term complications in women undergoing implant-based breast reconstruction with use of an acellular dermal matrix (ADM). This study compared outcomes over 5 years in women undergoing breast reconstruction procedures with and without ADM.Methods:Complications data in patients enrolled in the prospective Continued Access Reconstruction/Revision Expansion trial were segregated by use of ADM versus no ADM in patients undergoing primary breast reconstruction or revision-reconstruction. Continued Access Reconstruction/Revision Expansion trial evaluated long-term safety and effectiveness of shaped, textured, silicone implants.Results:Of the 9502 women, 257 had primary (n = 160) or revision-reconstruction (n = 97) with ADMs; 9245 had primary (n = 6977) or revision-reconstruction (n = 2268) without ADMs. Capsular contracture rates in primary reconstruction were lower with ADM than without at year 5 (3.2% versus 7.4%); rates were similar at year 1 (≤2.4%). Capsular contracture rates in revision-reconstruction were lower with ADM than without at year 5 (1.4% versus 8.9%); rates were similar at year 1 (≤2.5%). Seroma rates were low and sustained for all cohorts throughout the 5 years (≤2.9%). Reoperation rates increased over time in all cohorts, with similar rates between groups (2.4%–47.3% from week 4 to year 5 across cohorts). Other trends over time included lower rates for asymmetry and implant malposition with ADM than without.Conclusion:These long-term data suggest that the use of ADM in breast reconstruction procedures may provide a benefit in reducing complications, such as capsular contracture, and may sustain low rates of seroma.