Er,Cr:YSGG laser has been used safely on both oral soft tissue and tooth structure. Using defocused mode for pretreated enamel before bonding to composite resin was claimed as an alternative method to conventional acid etching. Objective: To compare shear bond strength of composite resin to Er,Cr:YSGG laser pretreated enamel to acid etched enamel. Methods: Thirty-six human premolars were divided into two groups. In group1, the teeth underwent enamel preparation by using 35% phosphoric acid (Scotchbond® etchant, 3M ESPE) for 20 seconds. The enamel of the teeth in group 2 were treated with Er,Cr:YSGG laser (Millennium®, Biolase Technology) 4.5 watts of power output for 15 seconds. All pretreated enamel in both groups was bonded with bonding agent (Single Bond®, 3M ESPE) to the prefabricated size of composite resin cubes. Universal testing machine was used to test the shear bond strength. Results: The mean shear bond strength in acid etched group was 18.68±8.33 (S.D.) MPa and in laser treated group was 8.32±5.11 (S.D.) MPa. Conclusion: Shear bond strength of pretreated enamel with 4.5 watts Er,Cr:YSGG laser was significantly less (p<0.001) than conventional acid etch enamel preparation as tested by unpaired t-test.