We examined the link between action planning and motor imagery in 6- and 8-year-old children. Action planning efficiency was assessed with a bar transport task. Motor imagery and visual imagery abilities were measured using a hand mental rotation task and a number (i.e., non-body stimuli) mental rotation task, respectively. Overall, results showed that performance varied with age in all tasks, performance being progressively refined with development. Importantly, action planning performance was correlated with motor imagery, whereas no relationship was evident between action planning and visual imagery at any age. The results showed that the ability to engage sensorimotor mechanisms when solving a motor imagery task was concomitant with action planning efficiency. The present work is the first demonstration that evaluating the consequences of the upcoming action in grasping depends on children's abilities to mentally simulate the response options to choose the most efficient grasp.