The purpose of the present study was to evaluate enamel bond strength of a composite resin material after hydrogen peroxide bleaching, activated by a diode laser (LaserSmile), an ozone device (HealOzone), a light-emitting diode (BT Cool whitening system), and a quartztungsten- halogen device (Hilux Ultra Plus). Fifty extracted caries-free permanent incisors were used in this study. Thirty-eight percent hydrogen peroxide gel was applied to sound, flattened labial enamel surfaces and activated by different sources. Enamel surfaces that had received no treatment were used as control samples. Bonding agent was applied according to the manufacturer's instructions and the adhesion test was performed according to ISO/TS 11405. Statistical analysis showed significant influence of the different activation techniques of hydrogen peroxide on shear bond strength to enamel (ANOVA, LSD, P 0.05). The data in this in vitro explorative study suggest that activation of hydrogen peroxide by different sources may further affect the shear bond strength of subsequent composite resin restoration to enamel. Within the limitations of this in vitro study, further studies examining the structural changes of activated hydrogen peroxide-treated enamel are needed. Due to the different activation methods' duration of light irradiation, power densities, and dehydration effects, longer time periods may be needed before application of adhesive restorations to enamel, compared with non-activated bleaching.