Aim: The aim of this study was to compare different dentin treatments and adhesive systems on shear bond strength (SBS) of composite to superficial dentin. Materials and methods: In this in vitro experimental study, 60 extracted human upper premolars were cut 0.5 mm deep under occlusal DEJ and were randomly divided into six groups (n = 10) based on the method of dentin treatment and adhesive system: (A) two steps self-etch adhesive system (Clearfil SE bond) and (B) two steps of total etch bonding system (Adper single bond 2). (C) 10% papain + Clearfil SE bond. (D) 10% papain + Adper single bond 2. (E) 6% bromelain + Clearfil SE bond. (F) 6% bromelain + Adper single bond 2. Then, a plastic mold was placed on dentin and filled with resin composite. Shear bond strength (MPa) was tested by a universal testing machine (Zwick/Roell Z020, Germany), and the data were statistically analyzed by two-way ANOVA and Tukey's test (p < 0.05) and were applied for mean comparison. Results: A significant difference was detected in the SBS evaluation between the applied adhesive systems (p = 0.0007). The SBS was also significantly affected by the interaction of treatment and etching techniques (p = 0.028). The group with 10% papain as a deproteinizing agent before the self-etching adhesive system showed the highest SBS (p = 0.029). There were no significant differences considering the specimens exposed to papain before the total etch adhesive system (p = 0.13), and the specimens were exposed to bromelain enzyme before self-etch and total etch adhesive systems (p = 0.25, p = 0.84, respectively). Conclusion: Papain enzyme treatment with the self-etch adhesive system increased the SBS value. Additionally, the application of bromelain enzyme as dentin treatment before two adhesive systems and papain before total etch adhesive system had no effect on the SBS of composite to superficial dentin. Clinical significance: Application of adhesive systems and dentin treatment can influence the bond strength.