Background: Pregnant women are vulnerable to oral disease due to physiological, hormonal, and dietary alterations. The aim of the present study was to evaluate the impact of the educational program according to the Health Promotion Model (HPM) on the oral health prevention behavior of pregnant women. Study Design: A randomized controlled trial. Methods: This study was performed on 105 pregnant women visiting health centers located in Arak from February to November 2022. The subjects were randomly assigned to intervention (n=54) and control (n=51) groups. A reliable and valid questionnaire according to HPM constructs was used to collect the data. The pre-test was conducted in the groups. The intervention group received the educational program in 9 educational sessions (from 12 to 24 weeks of pregnancy). Then, the post-test was conducted in the 36th week of pregnancy in the groups. Finally, the data were analyzed by SPSS software (version 18) and using independent t-test, paired t-test, and Chi-square test. Results: There were statistically significant differences between the intervention and control groups regarding perceived benefits (24.68±3.63 vs. 26.57±3.67, P=0.009), perceived barriers (7.31±3.14 vs. 5.81±3.59, P=0.025), positive affect (10.50±1.66 vs. 11.29±1.34, P=0.009), negative affect (1.59±0.223 vs. 1.40±1.51, P=0.006), commitment to the action plan (4.05±1.92 vs. 4.77±1.50, P=0.034), and tooth brushing time (2.29±0.72 vs. 2.74±0.48, P<0.001). However, no significant difference was observed regarding the tooth brushing frequency (2.05±0.58 vs. 2.07±0.66, P=0.901) after the intervention. The brushing time for 2-3 minutes in the intervention group increased from 51.85% to 75.92% after the intervention. Conclusion: HPM-based education was effective in promoting the duration of tooth brushing in pregnant women. However, it had no effect on the tooth brushing frequency.