Introduction: The use of different models play a significant role in health education and its promotion. Therefore, the present study aims to investigate the effect of the Theory of Planned Behavior (TPB) on early dental decay in elementary students. Methods: This study was a single-blinded, cluster randomized controlled trial, in which 470 elementary students in the fourth, fifth and sixth grades in Saveh, Iran were participated. A demographic questionnaire and a 5-item questionnaire consisting of questions on awareness, attitude, practice, tooth brushing, diet and referring to dentist, were used to data collection. The samples of the intervention (n=234) and control (n=236) groups filled out the questionnaires before intervention (pre-test), immediately after intervention and one month after intervention. The educational intervention based on the TPB was held in three 45-minute sessions. Finally, the data were analyzed, using the SPSS version 13. For analyzing, the Independent t-test, Chi-square, and repeated measures ANOVA were used. Results: This study showed that there is a significant difference in the mean scores obtained from knowledge, attitude, subjective norm, perceived behavioral control, behavioral intention and behavior among students in the experimental group (immediately after and one month after the intervention) and students in the control group. Conclusion: The results of this study showed that using of TPB, as a framework for providing behavior-led training, can be effective in promoting oral and dental health of students. Nurses as an important member of the treatment team can use the results of this study in school health programs.