Micro-morphological and organic-inorganic changes of dental structure as well as the effect of hydrogen peroxide on polymerisation of composite materials cause lower adhesion, i.e. poor bond quality between composite material and bleached tooth. The aim of this study was to determine the effect of different concentrations of carbamide (16%, 20% and 30%) and 35% hydrogen peroxide on bond strength of the composite materials and bleached endodontically treated teeth. Methods: The current study included 40 extracted human endodontically treated teeth. Internal bleaching was done using the “Walking bleach technique” method. The teeth were bleached with 16%, 20%, 30% carbamide or 35% hidrogen peroxide. After internal teeth bleaching, a class V cavity was prepared and restored with Tetric EvoCeram nanocomposite material. Microleakage was determined using dye method (silver nitrate) and measured on the incisal and gingival walls using stereoloupes. Results: The smallest dye penetration on the occlusal wall was found of teeth bleached with 20% carbamide peroxide (5,45 μm), and the largest dye penetration was on teeth bleached with 30% carbamide peroxide (7,25 μm). The smallest dye penetration on the gingival wall was found on teeth bleached with 16% carbamide peroxide (12,25 μm) and the largest dye penetration was on teeth bleached with 30% carbamide peroxide (20,00 μm). The difference was statistically significant (p 0.05). Conclusion: Microleakage was detected in all teeth restored with composite and bleached with the internal bleaching technique with 16%, 20%, 30% carbamide or 35% hydrogen peroxide.