Purpose: The purpose of this in vitro study was to determine the effect of air-abrasion pretreatment on microleakage of Class V resin composite restorations bonded with self-etching primers. Materials and Methods: A total of 54 Class V cavities prepared either with diamond burs or air abrasion (KCP 1000) was restored with resin composites using adhesive systems with self-etching priming agents (Clearfil Liner Bond 2 or Resulcin AquaPrime + Monobond) and thermocycled 2,500 times. The degree of dye penetration (0.5% methylene blue solution) was scored on an ordinal scale at 25X magnification on longitudinally cut sections of the specimens. Wall adaptation at the tooth-restoration interfaces was evaluated under a SEM using replicas of the sectioned teeth. Results: Severe microleakage occurred at the gingival dentinal margins, and less microleakage was detected at the enamel cavity margins. Nonparametrical statistical analysis (H-test) demonstrated no significant differences in microleakage among the different groups. Comparison of dye penetration data and SEM findings showed that with both self-etching priming agents, microleakage occurred in the absence of gaps. Conclusion: Use of air abrasion in combination with self-etching priming agents cannot prevent microleakage at the dentin-resin interface of Class V resin composite restorations.