Objective: Existing research shows that sociodemographic factors are associated with dietary patterns among adolescents; however, little is known about when these relationships begin in children. The purpose of this study was to examine the relationship between dietary self-efficacy (SE) and dietary intake among children over time and by race/ethnicity, among students receiving a healthy eating and physical activity intervention. Design: Pretest-posttest questionnaire, before and after an 8-month intervention Setting: The study was conducted in a large Midwestern metropolitan area of the USA. Method: Students (N = 332, M[subscript age] = 9.1; SD = 0.61; female = 45%, Black = 46%) completed a questionnaire at the beginning (T1) and end (T2) of the school year. The Wilcoxon signed-rank test and a Mann-Whitney U test were used to determine if there were differences by group. Results: SE at T1 was associated with intake (p < 0.01 to p < 0.05; except whole grains). While there were not intervention effects over time in dietary self-efficacy or intake, findings suggest that healthy eating and self-efficacy differences do not exist in children when examined by race/ethnicity, except in the case of a composite healthy eating score with White students reporting a higher intake of healthy food and a lower intake of unhealthy food overall. Conclusion: Future research should examine when specific differences in healthy eating and SE emerge in children or adolescents in order to develop school, home and community-based interventions that effectively disrupt differences by race/ethnicity before they occur in adolescence.