Aim: The aim of this study was to evaluate the effects of multiple consecutive coatings of a one-step self-etch adhesive system (Clearfil Tri-S Bond) on the microtensile bond strength (MBS) to dentin. Methods and Materials: Nine caries-free human lower third molars were sectioned perpendicular to the long axis to expose the mid-coronal dentin. The teeth were separated into three experimental groups (n=3) according to the number of adhesive resin coats applied. In Group 1 one layer of Clearfil Tri-S Bond was applied according to the manufacturer's instructions. In Group 2 and Group 3 the adhesive was applied in two and three layers, respectively. In these two groups the first layer was applied according to the manufacturer's instructions but the second and third layers of adhesive were not light cured after application. After the placement of the composite, the teeth were sectioned to obtain approximately 1 mm2 beams for testing. Eighteen beams were prepared for each group using the 'non-trimming' method. The MBS values of all specimens were tested, and fracture modes were then determined using a stereomicroscope. Results: The mean MBS values (in MPa) of Group 1 (one coat of the adhesive) was significantly lower (p=0.04) than those of Group 3 (three applied coats of the adhesive). There were no statistically significant differences between Groups 1 and 2 and Groups 2 and 3. Conclusion: Within the limitations of this in vitro study the application of multiple coats of a one-step self-etch adhesive may provide an increase in bond strength compared to the application of only one coat of adhesive. Clinical Significance: Three consecutive coats of one-step self-etching adhesive application can improve MBS.