The aim of this study was to determine whether the addition of an autologous platelet-rich fibrin clot (PRF) to a modified coronally advanced flap (MCAF) (test group) would improve the clinical outcome compared to an MCAF alone (control group) for the treatment of multiple gingival recessions. Twenty subjects, presenting three adjacent Miller Class I or II multiple gingival recessions of similar extent on both sides of the mouth, were enrolled in the study. The mean recession value at baseline was 2.9 +/- 1.1 mm for test sites and 2.5 +/- 0.9 mm for control sites. Each patient was treated on both sides by an MCAF technique; the combination treatment (with a PRF membrane) was applied on the test side. Probing depth (PD), recession width, clinical attachment level (CAL), keratinized gingival width, and gingival/mucosal thickness (GTH) were measured at baseline and at 6 months post-surgery. Gingival recession was measured at baseline and at 1, 3, and 6 months post-surgery. Mean root coverage after 1, 3, and 6 months was 81.0% +/- 16.6%, 76.1% +/- 17.7%, and 80.7% +/- 14.7%, respectively, at the test sites and 86.7% +/- 16.6%, 88.2% +/- 16.9%, and 91.5% +/- 11.4%, respectively, at the control sites. Differences between the two groups were statistically significant at 3 and 6 months. At 6 months, complete root coverage was obtained at 74.6% of the sites treated with the control procedure but at only 52.2% of the experimental sites. At 6 months, the increase in GTH was statistically significant when comparing the test sites (from 1.1 +/- 0.3 mm at baseline to 1.4 +/- 0.5 mm at 6 months) to the control sites (from 1.1 +/- 0.3 mm at baseline to 1.1 +/- 0.3 mm at 6 months). In the case of PD, there was no significant difference between the two groups at 6 months, but a significant CAL gain in favor of the control group was observed at that time. MCAF is a predictable treatment for multiple adjacent Miller Class I or II recession-type defects. The addition of a PRF membrane positioned under the MCAF provided inferior root coverage but an additional gain in GTH at 6 months compared to conventional therapy.