The purpose of this study was to examine the longitudinal causal relationship among Korean students' past academic performance, self-efficacy beliefs, and academic achievement. The study used an autoregressive cross-lagged model to assess the casual ordering of self-efficacy beliefs and academic achievement in a representative sample of 1177 Korean students over a five-year period from the 8 to 12th grades. Results indicated that the academic performance of students from the first semester of the 8th grade positively predicted self-efficacy beliefs for the second semester of the 8th grade and that self-efficacy beliefs from the second semester of the 8th grade positively predicted the academic achievement of students for the first semester of the 9th grade; this pattern evidenced through to the 12th grade. A reciprocal relationship between self-efficacy beliefs and academic achievement was seen, such that the effect of past academic performance on self-efficacy beliefs was larger than the effect of self-efficacy beliefs on academic achievement. These findings point to the importance of integrating the reciprocal model into practice and utilizing interventions delivered by educators, school counselors, and school psychologists that target both self-efficacy and academic achievement. Future research is needed to evaluate interventions designed to address both self-efficacy and academic achievement.