Aims: To evaluate the effect of various aging periods and different surface preparation methods on microtensile bond strength (mu TBS) for composite repair. Materials and Methods: One hundred twelve composite resin blocks were formed using a nanohybrid composite resin. The samples were distributed into four groups according to surface preparation methods (n = 28): control (sound composite blocks); Er, Cr: YSGG laser; air abrasion; silicone carbide. All samples were then divided into four subgroups according to various aging periods: (i) No aging, (ii) 10,000 thermocycling, (iii) 30,000 thermocycling, and (iv) 50,000 thermocycling. Following surface preparation and aging procedures, surface topography of one sample from each group was evaluated under scanning electron microscope (SEM). The repair composites were bonded to the sample surfaces, using a three-step etch&rinse adhesive. Finally, thirty beams of size 1 x 1 x 8 mm from each group were subjected to mu TBS test and failure modes were determined. The data were analyzed using two-way ANOVA, Post-hoc Bonferroni, and Chi-square tests (P = 0.05). Results: When different surface preparation methods were evaluated together, no aging and 10,000 thermocycling groups displayed higher mu TBS values (P < 0.05). When all aging periods were evaluated together, the surface preparation with air abrasion provided higher mu TBS (P < 0.05). The interactions of various aging periods with different surface preparation methods revealed significant variations in repair mu TBS (P < 0.05). There were statistically significant differences on failure mode distributions among surface preparation methods (P < 0.001). SEM evaluations provided valuable outcomes that help to comment on the mu TBS findings. Conclusions: Different surface preparation methods, various aging periods, and the interaction of both affected the repair mu TBS of the tested nanohybrid composite resin.