Background/Aim: Increased knowledge, attitudes, and beliefs about a topic and behavioral capability and self-efficacy for healthy eating are often a precursor to behavior change. The purpose of this study is to determine the effectiveness of the multicomponent school-based program on children's healthy eating knowledge, attitudes, and self-efficacy for healthy eating, and on their eating habits over time. Method: Quasi-experimental (4 treatment, 2 comparison) in a metropolitan area using a pretest-posttest method. Participants were 628 fifth-grade youth (377 treatment, 251 comparison) with a mean age of 9.9 years. The Building Healthy Communities (BHC) program is an 8-month school-wide healthy school transformation program and includes six main components. Outcome measures include children's healthy eating knowledge, attitudes, self-efficacy, and behavior. Missing data were imputed, confirmatory factor analysis tested scale factor structure, and path analysis determined a parsimonious path explaining behavior change. Results: The Student Attitudes and Self-Efficacy (SASE) scale had good measurement model fit. BHC group's healthy eating knowledge and behaviors increased significantly, while SASE remained moderate. For both groups, the students' knowledge and SASE significantly predicted their healthy eating behaviors; however, the intervention group accounted for a greater amount of variance (35% vs. 26%). Discussion: The BHC program was effective in improving healthy eating knowledge and behavior among youth, and the relationship between variables did not vary by group. Healthy eating knowledge is a significant predictor of both future knowledge and behavior.