This study evaluated the influence of the irradiation with a short-pulse Er:YAG laser on the adhesion of composite resin to sound and eroded dentin (SD and ED). Forty-six samples of occlusal dentine, obtained from human molars, had half of their surface protected, while the other half was submitted to erosive cycles. Afterward, 23 samples were irradiated with Er:YAG laser, resulting in four experimental groups: SD, sound irradiated dentine (SID—Er:YAG, , 2 Hz, 80 mJ, and ), ED, and eroded irradiated dentin (EID—erosion + Er:YAG laser). A self-etching adhesive system was used, and then cylinders of composite resin were prepared. A microshear bond strength test was performed after 24 h storage (). The morphology of SD and ED, with or without Er:YAG laser irradiation, was evaluated under scanning electron microscopy (). Bond strength values (MPa) were subjected to analysis of variance followed by Tukey’s test. Statistically significant differences were found among the experimental groups: SD (), SID (), ED (), and EID (). Even though erosion reduces the adhesion to dentin, the surface irradiation with a short-pulse Er:YAG laser increases adhesion to both ED and SD.