Introduction: Pit-and-fissure caries accounts for 80-90% of total caries occurrence. Fissure sealant has an important role to prevent caries in deep pit and fissure. Resin is one of the materials that being used for fissure sealant, among them are resin-based sealant and resin modified glass ionomer sealant (RMGIC). Acid activity in soft drinks may deteriorate surface hardness of the restorative material. The aim of this research is to find the changes of surface mi-crohardness of resin-based sealant and RMGIC after immersion in soft drinks. Methods: The objects that being used in this research are 12 samples of resin-based sealant and 12 samples of RMGIC. The samples are divided into 6 groups, which are two control groups that immersed in the distilled water, and four treatment groups that immersed in different brand of soft drink for 2 minutes every day for 21 days. Results: Both material show decreasing value of microhardness after 21 days immersion. The data were analyzed using One-way ANOVA and show 0,0 value, which means there is significant difference between surface microhardness value of resin-based sealant and RMGIC (p<0.005). The resin-based sealant was the most affected by acidic environment after immersion. Conclusion: The effect of soft drinks on the surface microhardness of restorative materials depends on the composition of the material. In this study, resin-based sealant has lower surface microhardness value compared to RMGIC after immersion in soft drinks.