Background: Oral health poses significant challenges, particularly among preschool children, emphasizing the critical role of mothers in preventive care. Self-efficacy, as a determinant of behavior, holds promise in shaping oral health practices. Objectives: The present study was conducted to determine the effect of Bandura's self-efficacy strategies on the fluoride varnish therapy behavior of mothers of preschool children. Methods: This intervention study, conducted from 2021 to 2023, involved 88 mothers with children aged 3 to 6 years. Participants were randomly divided into intervention and control groups. Data collection included a demographic questionnaire, a researcher-developed self-efficacy assessment tool, and an observational checklist of mothers' fluoride varnish therapy behavior. The intervention comprised educational sessions focusing on self-efficacy strategies. Data were analyzed with descriptive and inferential statistics in SPSS software version 20. Results: Before the intervention, there were no significant differences in self-efficacy scores between the intervention and control groups (Cohen's d = 0.18). Similarly, there were no significant differences between the two groups in the varnish therapy behavior score of the mother before the intervention (Cohen's d = 0.05). However, two months later, significant improvements were observed in both self-efficacy scores (Cohen's d = 2.28) and fluoride varnish therapy behavior (Cohen's d = 3/32) among mothers in the intervention group compared to controls. Conclusions: This study underscores the pivotal role of self-efficacy strategies in empowering mothers to effectively engage in fluoride varnish therapy behavior, and highlights the significant improvements observed in both self-efficacy and varnish therapy behavior that emphasize the educational interventions aimed at enhancing mothers' self-efficacy, ultimately contributing to improved oral health outcomes for children.