Recent evidence in adults indicates that object perceptual processing is affected by the competition between action representations. In the absence of a specific motor plan, reachable objects associated with distinct structural (grasping) and functional (using) actions (e.g., calculator) elicit slower judgments than objects associated with similar actions (e.g., ball). This effect is believed to reflect the cost entailed by the conflict between action representations. The present study aims to identify age-related changes in this conflict cost and investigate its underlying mechanisms. Five age groups from 8 to adulthood participated (n = 119). Participants performed perceptual judgments on different 3D objects in a virtual environment in order to assess their conflict cost (Experiment 1). Action priming effects and Simon effects were further assessed in the same participants as independent indices of the ability to activate action representations and to monitor conflict, respectively (Experiments 2 and 3). Experiment 1 demonstrated that the conflict cost is present in children as young as 8 and follows a non-linear, U-shaped developmental trajectory between 8 and adulthood. Experiments 2 and 3 indicated that action priming effects showed a similar U-shaped curve, whereas Simon effects were stable across age groups. Action priming effects further predicted conflict costs at 10. Results suggest that the conflict cost relies on the ability to activate action representations from visual objects, which undergoes important changes during early adolescence. The role of general conflict monitoring abilities in conflict cost development requires further investigation. The findings will fuel models of action selection and embodied views of development.