Objectives: The purpose of this study was to examine whether demographic and socio-economic characteristics, health behaviors and health status are related to academic achievement in Korean adolescents. Methods: Data from the 14th Korea Youth Risk Behaviors web-based Survey(KYRBWS) administered in 2018 were analyzed; 60,040 students in middle and high school participated in the survey. It was conducted frequency analysis, Rao-Scott chi-square test and multiple logistic regression analysis after adjusted for variables such as age, school grade. Results: The significant influencing factors on academic achievement were family economic status, living with parents, subjective health status, smoking experience, alcohol use experience, eating breakfast, sleeping, internet use during weekdays, depressive symptom(p<.001). The odds ratio for achieving higher academic achievement compared with those who never smoked was 1.50(p<.001). Conclusion: I found that students’ undesirable health behaviors affect their academic performance. To improve academic achievement, I recommend intervention programmes such as school health promotion that reduce undesirable health related behaviors.