Background and Aim: Preparation of tooth structure by laser systems produces a surface with different characteristics. Therefore, selecting an appropriate bonding system is necessary to achieve the maximum bond strength. The aim of this study was to compare the bond strength of Adper Single Bond 2 adhesive and Single Bond Universal to dentin prepared by bur or laser. Materials and Methods: In this experimental study, 48 third molars were collected. The enamel was abraded by wet grinding to achieve flat surfaces of dentin. Samples were divided into 4 groups. Group 1: bur preparation + Single Bond Universal adhesive, Group 2: bur preparation + Adper Single Bond 2, Group 3: Er:YAG laser preparation + Single Bond Universal adhesive and Group 4: Er:YAG laser + Adper Single Bond 2. Nanocomposites were bonded to the samples. The shear bond strength was measured. Failure mode was evaluated under a stereomicroscope. Data were analyzed using twoway ANOVA. The level of significance was considered as 0.05. Results: The shear bond strength of the laser group was significantly lower than that of bur group (P<0.001). No significant difference was observed in shear bond strength regarding the type of adhesive used (P>0.05). The failure mode in all groups was mainly mixed. Conclusion: Preparation of dentin by Er: YAG laser decreased the bond strength in comparison to diamond bur preparation. The type of adhesive did not affect the bond strength, regardless of the preparation method.