Purpose: This study aimed to evaluate the effects of gargling with S-solution and gargling with A-solution on salivary pH, coated tongue, and dental plaque index in preschool children. Methods: Non-equivalent control group pretest-posttest design was used to select the participants. 99 preschool children were divided into three groups. Dependent variables were recorded at baseline, 30 minutes, and 7 days after the first treatment was given. The data were analyzed using X2-test, ANOVA, and repeated measures of ANOVA. Results: There were no significant differences in dependent variables in pre-test. However, the salivary pH in the S-solution group had significantly increased after 30 minutes (p<.05) and then again 7 days (p<.01) after the first treatment. Also, the S-solution and A-solution groups had greater decrease in dental plaque index after 30 minutes and again 7 days after the first treatment (p<.001) than the control group. With respect to coated tongue, there were no significant differences among the three groups. Conclusion: The results of this study indicate that essential oil gargling after brushing is helpful in improving oral health due to auxiliary oral hygiene effects with natural products. Specifically, gargling with S-solution is more effective than A-solution on oral health in preschool children by neutralizing salivary pH and reducing dental plaque index.