Aim: This study evaluated the microtensile bond strength (MTBS) of an orthodontic adhesive to water-aged composite surfaces using different surface treatments. Subjects and Methods: Twelve composite blocks (10 mm x 10 mm x 5 mm) were fabricated and randomly divided into two groups. Half of the specimens were stored in distilled water for 1 day, and the other specimens were stored for 30 days. The specimens were randomly assigned to six groups according to surface treatments (n = 15): Group 1, control (no treatment); Group 2, phosphoric acid; Group 3, diamond bur; Group 4, diamond bur + phosphoric acid; Group 5, laser; and Group 6, laser + phosphoric acid. One coat of orthodontic adhesive was bonded to one surface of composite blocks, and a microhybrid composite resin was bonded to the surfaces via a Teflon mold. Bond strength was evaluated using an MTBS test. Surface topography was evaluated using scanning electron microscopy (SEM) analysis. The data were analyzed using one-way analysis of variance, Tamhane post-hoc test, and independent sample t-tests (P < 0.05). Results: Bond strength values tended to decrease in all groups (with the exception of Group 2) after storage in water for 30 days (P < 0.05). Laser and diamond bur application (with or without phosphoric acid) enhanced the bond strength. Conclusions: An Er,Cr:YSGG laser application may be a feasible alternative to diamond bur for enhancing the bond strength of orthodontic adhesive to composite resin.