This study aims to evaluate the impact of a social cognitive theory (SCT)-based intervention on dietary behaviors and behavioral determinants. A randomized controlled trial was conducted with 230 adolescent girls (13-15 years old) in the intervention (n=115), and control group (n = 115), in Isfahan, Iran. Interventions were focused on changing SCT determinants including, knowledge, self-efficacy, intention, situation, self-regulation, social support, outcome expectations and expectancies. The intervention program included multicomponent intervention packages for adolescents, parents and teachers. A self-report questionnaire was used to assess dietary behaviors and SCT determinants at 3- and 6-month follow-ups. At 3- and 6-month follow-ups, differences between the intervention and control groups were reported in terms of the changes in all behavioral determinants and dietary behaviors. The changes in most behavioral determinants were significantly associated with the changes in dietary behaviors. The results showed that the nutrition education intervention based on SCT is effective in improving adolescents' dietary behaviors but dietary behaviors of adolescents in this study not yet reached to ideal status.