The aim of this study was to investigate the relationship between motor skills (fine and gross) with academic performance (reading and math) by considering the mediating role of cognitive ability (processing speed and working memory). The sample consisted of 200 children (50% girls) aged six and seven years from Tehran who participated in this study in the available academic year of 2017-2018. Fine and gross motor skills were assessed using the Bronnix-Ozeretsky-II test, academic achievement was assessed using the Wechsler Individual Success Test, and cognitive ability was assessed using the Wechsler Intelligence Scale. The results showed a positive relationship between all components of motor skills, cognitive ability and academic achievement (P <0.05). Structural equation modeling analysis also revealed that processing speed and working memory improve academic performance by being influenced by fine and gross motor skills. Therefore, processing speed and working memory play a mediating role in this regard. The results of this study show that in the early years of school and in preschool age, attention to motor skills can play a significant role in improving academic performance. Hence the importance of improving motor skills becomes more apparent.