Aim: To evaluate the long-term outcomes of Acellular Dermal Matrix (ADM) with Coronally Advanced Flap (CAF) or Tunnel technique (TUN) in the treatment of multiple adjacent gingival recessions (MAGRs). Material and methods: Nineteen of the original 24 patients contributing to a total number of 33 sites for CAF and 34 for TUN were available for the 12 years follow-up examination. Recession depth, mean root coverage (mRC), keratinized tissue width (KTW), gingival thickness (GT) were evaluated and compared with baseline values and 6-months results. Regression analysis was performed to identify factors related to the stability of the gingival margin. Results: A highly significant drop in mRC was observed for both groups from the 6 months timepoint to the 12 years recall (p < .001). While there were no statistically significant differences between the two groups in terms of Clinical Attachment Level (CAL), KTW, GT changes and Root Coverage Esthetic Score at each timepoint (p > .05). KTW ≥ 2 mm and GT ≥ 1.2 mm at 6-months were two predictors for stability of the gingival margin (p = .03 and p = .01, respectively). Conclusions: A significant relapse of the gingival margin of MAGRs treated with CAF or TUN + ADM was observed after 12 years.