Objectives: The relationship between physical fitness and academic achievement in children has received much attention, however, whether executive functioning plays a mediating role in this relationship is unclear. The aim of this study therefore was to investigate the relationships between physical fitness, executive functioning, and academic achievement, more specifically to test whether the relationship between physical fitness and academic achievement is direct or indirect, via executive functioning. Design: Cross-sectional. Method: This study examined 263 children (145 boys, 118 girls), aged 7-12 years, who performed tests on physical fitness, executive functioning, and academic achievement. Results: In a structural equation model linking physical fitness to executive functioning and academic achievement there was a significant relationship between physical fitness and executive functioning (r = .43, R-2 = .19) and academic achievement (r = .33, R-2 = .11). Adding a relationship from executive functioning to academic achievement resulted in a non-significant direct link between physical fitness and academic achievement (r = -.08, R-2 = .006). However, a significant indirect relation through executive functioning persisted. The indirect relation between fitness and academic achievement (r = .41), was stronger than both the direct and total relation (r = .33). Conclusion: Executive functioning thus served as a mediator in the relation between physical fitness and academic achievement. This highlights the importance of including executive functioning when studying the relationship between physical fitness and academic achievement in children. (C) 2014 Elsevier Ltd. All rights reserved.