Objective. The main objective of this study was to evaluate the effects of an at-home and two in-office (chemically activated and KTP laser-activated) bleaching methods on the microleakage of composite resin restorations bonded with etch-and-rinse and self-etch adhesive systems. Materials and methods. Class V cavity preparations were performed on 96 premolars and teeth were divided into two groups according to the two adhesive systems (etch-and-rinse and self-etch). After cavities were restored with an adhesive systems and composite resin, they were submitted to thermocycling procedures. Teeth were divided into four sub-groups according to the bleaching systems (control, at-home bleaching, chemically activated office bleaching and KTP laser-activated office bleaching). After the bleaching procedure, teeth were evaluated for marginal leakage. All data were analyzed using the Mann-Whitney U and Kruskal-Wallis tests (p < 0.05). Results. The results of the present study showed that the control group presented lower microleakage values compared with the groups treated with bleaching agents, except for the chemically activated in-office bleaching. When the scores of microleakage at the enamel and gingival margins of the four groups were compared, the differences among the groups were found to be statistically significant (p < 0.05). Comparing the gingival and enamel margins in each group, statistically significant differences were found in the at-home group (p < 0.05) and no significant differences were seen in the other groups (p > 0.05). No significant difference was found between the adhesive systems after treatment with the same bleaching techniques. Conclusion. Under the conditions of this study, microleakage of composite resin restorations differs according to the bleaching methods used and no difference was found between the adhesive systems.