ObjectiveTo investigate the impact of social cognitive determinants on healthy eating behaviors among adolescents, with a specific focus on gender differences. DesignCross-sectional analysis of survey data. SettingBangkok, Thailand. ParticipantsA total of 1,200 undergraduates from public and private universities. Main Outcome MeasuresDependent variable: healthy eating behaviors measured by the total score of 11 items adapted from the Australian Dietary Guideline Index. Independent variables: self-efficacy, intentions, outcome expectations, perceived benefits, perceived barriers, situations, social support from parents and guardians, and social support from peers (measured by 54 Likert-type items). AnalysisMultiple linear regressions (α and P < .01). ResultsSelf-efficacy, intentions, perceived barriers, and situations had statistically significant relationships with healthy eating behaviors (ß = .17, .16, −.15, and .19, respectively). The predictor variables explained 18.1% of variance. Healthy eating in male adolescents was best predicted by perceived barriers, whereas that in female adolescents was best predicted by situations. Conclusions and ImplicationsThese results indicate that relevant agencies should deliver gender-specific approaches to promote healthy eating in adolescents. The findings demonstrate the need for further studies to explore a broader range of factors influencing adolescent eating behaviors.