Imitation is thought to require a perception-action matching process that utilizes the “mirror neuron” system, but other cognitive functions such as error detection may also be required for even simple imitation. We sought to explore the core neural substrate of imitation by examining the imitation of simple finger actions using fMRI. Participants observed one of two actions and were instructed to imitate the action they observed, or to perform the alternative non-matching action. The contrast between imitation and non-matching actions was associated with activation in areas previously associated with imitation and “mirror neuron” functioning, including insula, intraparietal sulcus, dorsal premotor cortex, and superior temporal gyrus. Imitation was also specifically associated with activity in areas of prefrontal cortex, lateral orbitofrontal cortex (OFC), amygdala, red nucleus, thalamus, hippocampus, and substantia nigra. We suggest that lateral OFC responds to action-perception mismatch and other clusters reflect working memory, motor planning, associative learning, and visuo-motor integration of goal-directed action. Although computational models have predicted integration of these functions to enable imitation, their specific brain bases have not previously been identified. Together they offer a potentially powerful means through which matching one’s actions to those of others can lead to behavioral modification and development.