To evaluate parent knowledge and belief changes following the MySmileBuddy (MSB) early childhood caries (ECC) intervention. Pre- and post-intervention surveys were completed by 669 parents of children with visually-evident ECC from among 977 participants in a 6-12-month pragmatic community-based caries management trial administered by community health workers (CHWs). Six domains of knowledge about caries and motivating and facilitating determinants were assessed via 26 survey items. Principal components analysis and reliability testing reduced dataset dimensionality. Parent and CHW characteristics were analyzed as potential moderators. Paired T-tests measured pre-to-post-intervention changes. Generalized estimating equations accounted for within-participant correlation with significance set at p < 0.05. Twenty items consolidated into five factors (saliva, hygiene, diet, seriousness/susceptibility, and outcome expectations). Six additional items were evaluated individually. Positive post-intervention changes (p < 0.0001) were observed across all factors and all but one individual item (tooth decay is very common). Greatest knowledge increases related to caries as a bacterial disease in two measures, the saliva factor and a single caries belief item tooth decay is an infectious disease (0.59 unit increase, 95% CI [0.55, 0.64] and 0.46 unit increase, 95% CI [0.4, 0.51], respectively), and in the value of fluoridated water over bottled (0.46 unit increase, 95% CI [0.39-0.53]). Most parents improved knowledge of ECC salivary (72%) and dietary risks (57%), and preventative hygiene behaviors (59%). MSB enhanced knowledge and beliefs about caries and confirmed hypothesized mediators of behavior change among parents of high-risk children. Engaging peer-like CHW interventionists may have moderated intervention effects, warranting further exploration.