Purpose: This descriptive correlation study was done to investigate adolescent behavior that promotes health and to identify factors influencing this behavior. Method: The participants (702) were a conveniently selected sample of second grade high school students. Data were gathered by self-administered questionnaires and the collected data were analyzed using descriptive statistics and stepwise multiple regression with the SPSS program. Results: 1) The score for health-promotion behavior was 2.49 (total possible score = 4). By subcategories, emotional support was the highest (3.02). 2) Of the factors influencing health-promotion behavior, self-efficacy was found to account for 37.5% of the variance, followed by family function, social support, perceived health status and internal health locus of control. Overall, these factors accounted for 50.6% of the variance. Conclusion: The findings of this study showed that health-promotion behavior in adolescents was slightly above average. As self-efficacy and family function were identified as major factors in predicting health-promotion behavior, there is a need to consider interventions that will improve self-efficacy and family function.