Objective: Previous studies have shown that academic achievement has a significant effect on juvenile delinquency, with the reverse reported as well. This study, therefore, examined the reciprocal causal relationships between academic achievement and juvenile delinquency. Methods: The participants were 3449 Korean adolescents (mean age 13.2 years, standard deviation (SD) = 0.4 at Time 1) from the Korea Youth Panel Survey. They were followed from the 8th to the 11th grade. A cross-lagged autoregressive model with four-year longitudinal data was used for the analysis. Results: For all grades (Time 1 through Time 4), juvenile delinquency was negatively affected by low academic achievement, while no effects of delinquency on academic achievement were indicated. Conclusion: There was a significant prediction from academic achievement for juvenile delinquency, rather than reciprocal influences between academic achievement and juvenile delinquency among Korean adolescents, which is different from Western counterparts. This study contributes to theoretical understanding of relations between academic achievement and delinquency in diverse cultural settings and interventions to promote optimal social health.