The ability to attribute mental states to others, and therefore to predict others' behavior, is particularly advanced in humans. A controversial but untested idea is that this is achieved by simulating the other person's mental processes in one's own mind. If this is the case, then the same neural systems activated by a mental function should re-activate when one thinks about that function performed by another. Here, using functional magnetic resonance imaging (fMRI), we tested whether the neural processes involved in preparing one's own actions are also used for predicting the future actions of others. We provide compelling evidence that areas within the action control system of the human brain are indeed activated when predicting others' actions, but a different action sub-system is activated when preparing one's own actions.