Abstract: OBJECTIVES: Previous studies have shown that a higher level of physical fitness (PF) and a healthy weight status are associated with better academic performance.However, as most of these studies were cross-sectional and conducted in foreign countries, the longitudinal relationships between these factors and academic performance remain unclear, especially in Japan.Thus, this study aimed to determine the longitudinal relationships between PF and weight status and the academic performance of Japanese junior high school students.METHODS: A total of 301 junior high school students (male, 158; female, 143) participated in this study.The data of study variables were collected at 1st and 3rd years of junior high school, and were used for analyses.The academic performance was evaluated using the total grade point of eight school subjects (GP8).The body mass index (BMI) and squared value of BMI (BMI 2 ) were used as weight status variables.PF was assessed by performing a 20-m shuttle run test.RESULTS: After controlling for gender, maternal education history, GP8 at 1st year, PF at 1st year, weight status variables at 1st year, and the PF and BMI 2 at 3rd year were significantly associated with GP8 at 3rd year (PF at 3rd year, β = .11,p = .03;BMI 2 at 3rd year, β = -.11,p = .046;R 2 = .73,p < .001).CONCLUSION: Increasing PF and maintaining a healthy weight would assist in increasing the academic performance of Japanese junior high school students.