This double-blind randomized clinical trial evaluated the influence of pre-treatment with proanthocyanidins (PA) from grape seed extract on the clinical behavior of a simplified etch-and-rinse adhesive placed in non-carious cervical lesions (NCCLs) over 6- and 24-months. A total of 135 restorations were randomly inserted in 45 subjects. The NCCLs were etched with 37 % phosphoric acid for 15 s and distributed into 3 groups: Control (PA0) - adhesive ExciTE F applied as per the manufacturer's recommendations; PA2 and PA5 groups - 2 wt% and 5 wt% PA solution, respectively, were applied for 60 s and washed for 30 s prior to application of the adhesive. The resin composite was placed incrementally and light-cured. The restorations were evaluated at baseline, 6 months (6 m) and 24 months (24 m) using both the FDI and USPHS criteria. Statistical analyses were carried out using Friedman repeated-measures analysis of variance by rank and the Wilcoxon test (α = 0.05). The retention rates were 98 % (PA0), 98 % (PA2) and 83 % (PA5) after 6 m and 93 % (PA0), 89 % (PA2) and 70 % (PA5) after 24 m. Only PA5 resulted in a significant lower retention rate at 6 m and at 24 m compared with that of baseline (p = 0.03). All groups resulted in a significantly worse marginal adaptation and marginal staining for the FDI criteria when the baseline vs. the 24 m recall data were compared. These differences were considered clinically acceptable under the FDI criteria. The application of PA as a primer did not result in clinical advantages after 24 m of clinical service, regardless of the concentration used. It has been reported that PA, a collagen crosslinking agent, increases the durability of the dentin-resin interface. However, no effects were found clinically after 24 months.