To assess the effectiveness of a child care center-based parent and teacher healthy lifestyle role-modeling program on child nutrition and physical activity outcomes. Child care centers (N = 28) serving low-income families were randomized to intervention or control arms. Intervention centers (N = 12) implemented (1) menu modifications, (2) a child's healthy lifestyle curriculum, and (3) an adult (teacher- and parent-focused) healthy lifestyle role-modeling curriculum. Control centers (N = 16) received an attention control safety curriculum. Nutrition and physical activity data were collected at the beginning (T1) and at the end (T2) of the school year. Exploratory factor analysis identified positive and negative nutrition and physical activity practices by children, parents, and teachers. Intervention parents' baseline (β = .52, p < .0001) and school year consumption (β = .47, p < .0001) of fruits/vegetables significantly increased their children's consumption of fruits/vegetables from T1 to T2. Intervention parents significantly influenced a decrease in children's junk food consumption (β = -.04, p < .05), whereas control parents significantly influenced an increase in their children's junk food consumption (β = .60, p < .001) from T1 to T2. Control children showed a significant increase in junk food consumption (β = .11, p = .01) and sedentary behavior (β = .09, p < .005) from T1 to T2. Teachers did not significantly influence preschool-age children's nutrition or physical activity patterns from T1 to T2. Parent nutrition and physical activity patterns significantly influence their preschool-age children's consumption of fruits/vegetables, junk food, and level of sedentary behavior. Future obesity prevention intervention efforts targeting this age group should include parents as healthy lifestyle role models for their children.