Does tool use share syntactic processes with language? Acting with a tool is thought to add a hierarchical level into the motor plan. In the linguistic domain, syntax is the cognitive function handling interdependent elements. Using functional magnetic resonance imaging, we detected common neurofunctional substrates in the basal ganglia subserving both tool use and syntax in language. The two abilities elicited similar patterns of neural activity, indicating the existence of shared functional resources. Manual actions and verbal working memory did not contribute to this common network. Consistent with the existence of shared neural resources, we observed bidirectional behavioral enhancement of tool use and syntactic skills in language so that training one function improves performance in the other. This reveals supramodal syntactic processes for tool use and language.