The purpose of this study was to evaluate the effect of a desensitizer on dentinal bond strength in cementation of composite resin inlay. Fifty four molar teeth were exposed the occlusal dentin. Class I inlay cavities were prepared and randomly divided into six groups. Control group ; no agent, Group 1 ; Isodan, Group 2 ; One-step, Group 3 ; All-Bond SE, Group 4 ; Isodan + One-step, Group 5 ; Isodan + All-Bond SE. Desensitizing agent and dentin bonding agents were applied immediately after the completion of the preparations. Impressions were then made. The composite resin inlays (Tescera, Bisco) were fabricated according to the manufacturers' guidelines. Cementation procedures followed a standard protocol by using resin cement (Bis-Cem, Bisco). Specimens were stored in distilled water at 37degrees C for 24 hours. All specimens were sectioned to obtained sticks with 1.0 x 1.0 mm2 cross sectional area. The microtensile bond strength (microTBS) was tested at crosshead speed of 1 mm/min. The data was analyzed using oneway ANOVA and Tukey's test. Scanning electron microscopy analysis was made to examine the details of the bonding interface. 1. Group 1 showed significantly lower microTBS than other groups (p<0.05). 2. There was no significant difference between the microTBS of Group 3 and Group 5. 3. The microTBS of Group 4 showed significantly lower than that of Group 2 (p<0.05). In conclusion, a desensitizer (Isodan) might have an adverse effect on the bond strength of composite resin inlay to dentin.