Objective: The purpose of this study was to investigate the effects of Erbium-doped: yttrium-aluminum-garnet (Er:YAG) laser pretreatment with different energy levels on the shear bond strength (SBS) of repairing composite materials. Background data: After long-term usage of composite resins in the mouth, they can need some repair. Repairing composite bonding so it attaches to the old restoration is important for clinical success. Methods: Sixty composite resin materials were used in this study. The aging procedure was performed with 6000 thermocycles in water from 5 degrees C to 55 degrees C. Different surface pretreatment methods [control (no surface treatment), sandblasting, laser treatment (energy level 75, 100, 200, and 300mJ)] were employed, for a total of six groups. Composite resins of the same kind as their substrates were adhered onto the conditioned substrates. The SBS test was used to assess the durability of all groups. Scanning electron microscopy (SEM) analysis was performed on a representative specimen in each group. Results: Among six surface-treated groups the lowest bond strength was observed in Group C (9.41MPa) (p<0.001). Group S exhibited the highest bond strength among all groups and showed significant difference from all other groups (33.41MPa) (p<0.001). In the Er:YAG test groups, bonding values showed varying results from 15.27 +/- 0.58 (Group L300) to 25.98 +/- 1.08 (Group L75) and showed significant increase when compared with control group (p<0.05). Conclusions: Altough the sandblasted group exhibited the highest test values, Er:YAG laser treatment on repair composite bonding to old composite may become an alternative to other surface treatment methods.