Statement of Problem: Bacteria are possibly left in the cavity after its preparation and can multiply after restoration. Thus, cavity disinfection prior to restoration can be effective if it does not interfere with adhesive resin adaptation.Purpose: To evaluate the effect of the application of chlorhexidine 2% on the microleakage of composite restorations using four adhesives.Methods and Material: In this experimental study, standard class V cavities were prepared in the buccal surfaces of 88 human premolars at the CEJ. The teeth were randomly divided into 8 groups, each containing 11 teeth.  Four adhesives of Scotchbond Multi-Purpose (SBMP), Excite (Ex), Clearfi SE Bond (CSEB) and iBond (iB) were used according to their manufacturer's instructions in the four control groups. In the four experimental groups, the same adhesives were used, but in the SBMP and EX groups, 2% chlorhexidine solution for 40 seconds was applied after the etching. In the CSEB and iB groups, chlorhexidine was applied before the adhesive application. The cavities were filled using Z250.  The samples were immersed in 0.2% methylene blue after finishing the restorations and thermocycling. Dye penetration was evaluated using stereomicroscope after sectioning. Kruskal-Wallis and Dunn tests were used for statistical analysis.Results: There were no significant differences among the microleakage of the control groups at the incisal and gingival margins ( p >0.05). Chlorhexidine did not affect the microleakage of the four adhesives.Conclusion: The results indicated that 2% chlorhexidine solution may not interfere with the sealing ability of the tested adhesives.Key words: Chlorhexidine, Marginal adaptation, Dentin adhesive