BACKGROUND: Sleep health is a prerequisite for mental and physical health. The family affects the sleeping habits of the child. OBJECTIVE: The purpose of this study was to investigate the theory of mothers’ planned behavior in predicting sleeping habits of toddlers. METHODS: The participants of this descriptive-analytical study were 120 mothers of 12- to 36-month-old children living in Razan, Hamadan province, Iran. Data were collected in three stages in order to develop a theory-based tool. Semi-structured qualitative interviews with mothers were conducted to investigate the application of theory in predicting mothers’ intention and behavior (n = 25). The face and content validity of the questionnaire was confirmed by a panel of experts. Test-retest method was used to determine the reliability of the questionnaire at 3 weeks interval (n = 25). Validity of Structural Convergence and Divergence with Factor Analysis, Internal Consent with Cronbach’s Alpha and predictive validity was determined by multiple regression coefficients (n = 120). RESULTS: The mean age of the children was 22.8 ± 7.5 months, 55% (66 children) were boys, the mean score of the children’s sleep questionnaire was 49 ± 6, and the children’s sleep duration was 9 ± 1 hour. Theoretical constructs have a positive and direct correlation with each other and with children’s sleep habits, which demonstrates the validity of the theory in predicting toddler sleep habits. Regression analysis showed that perceived behavioral control was the strongest predictor of sleeping habits of toddlers (𝛽 = 0.446) (P = 0.000). The theory of planned behavior can explain 30.5 to 25.7% of the variance of toddler sleep habits. CONCLUSION: While recommending more comprehensive studies, the findings of the study emphasize the application of the theory of planned behavior in identifying factors influencing sleep habits and designing child sleep improvement interventions.