ABSTRACT: Face masks continue to be a necessity until a large proportion of the population, including children, receive immunizations for COVID-19. The aim of this study was to investigate the relationship between parental attitudes and beliefs about masks and parent-for-child mask behavior using the Theory of Planned Behavior. We administered a survey in August 2020 to parents of school-aged children residing in the United States and Canada. Measures included sociodemographic variables for the parent and child, attitudes, norms, perceived control over children's mask use, intentions and enforcement of mask wearing among children (also titled "parent-for-child mask behavior"). Data were analyzed using structural equation modelling. We collected data from 866 parents and 43.5% had children with pre-existing conditions (e.g., allergies, anxiety, impulsivity, skin sensitivity, asthma) that made extended mask wearing difficult, as per parent's report. Among the full sample, negative attitudes (β = -0.20, p = .006), norms (β = 0.41, p = .002), and perceived control (β = 0.33, p = .006) predicted intentions. Norms (β = 0.50, p = .004) and intentions (β = 0.28, p = .003) also predicted parent-for-child mask use, while attitudes and perceived control did not. Intentions mediated the associations between attitudes, norms, perceived control, respectively, and mask behavior. Subgroup analyses revealed intentions as the key predictor of parent-for-child mask use among children with pre-conditions and norms as the key predictor among children without pre-conditions (i.e. healthy). Future public health messaging should target parental intentions, attitudes, norms, and perceived control about children's masks wearing.