Abstract : This research seeks to evaluate the effect of laser surface treatment of Er:YAG and Er,Cr:YSGG compared to acid etching on the micro-shear bond strength of nanohybrid flowable composite to dentin tested immediately after bonding and after thermocycling. Forty-eight extracted sound human molars were selected from persons aged between 25-45 years and the reason for extraction was either due to diabetes or periodontal disease. The shear bond strength after bonding of molar tubes using ER-YAG laser was normally distributed with mean of 6.29 standard deviation of 1.21. The micro-shear bond strength of acid etched bonded molar tubes was normally distributed with a mean of 5.08 and a standard deviation of 0.89. A total of 156 selected specimens were divided into three main groups based on surface treatment: ER:YAG laser surface treatment + universal adhesive system; ER;CR:YSGG + universal adhesive system; and acid etching + universal adhesive system (control group). Each group was further divided into four subgroups based on aging period: 24 hours in distilled water, 10,000 thermocycling cycles, 20,000 cycles, and 50,000 cycles. Both conventional acid etching and laser etching showed similar dentin bond strength values. All groups showed reduced bond strength after thermocycling Intragroup comparisons within the Er:YAG, Er:Cr:YSGG, and acid etch groups have shown statistically significant differences between different time periods. Laser etching offers a viable alternative to acid-etch, with fractographic analysis revealing adhesive failure in different surface treatments after just 10000 cycles, contrasting with acid-etched specimens.