The last decade has seen a surge of interest in the study of social brain functions. Research in this field, called social neuroscience, has been mostly carried out on human subjects by using a functional neuroimaging technique. This is largely because of the fact that humans have sophisticated social abilities and are capable of performing various demanding tasks in a scanner. However, given the limited spatiotemporal resolution inherent in the methodology, a systems neuroscience approach using macaque monkeys may provide a useful platform that promotes the understanding of social brain functions at the cellular level, thereby complementing neuroimaging techniques. Recently, it has been demonstrated to be technically feasible to train macaque monkeys to perform socially oriented behavioral tasks and directly examine cellular activity in their brains. In this paper, we review the literature on this new branch of social neuroscience. Emerging evidence now suggests that diverse aspects of social cognition, such as social valuation, gaze following, joint attention, monitoring of other's behavior, and social comparison are implemented by distributed neuronal networks, including the orbital, lateral, and medial sectors of the prefrontal cortex, premotor cortex, posterior parietal cortex, amygdala, and superior temporal sulcus. Continuing efforts in this research direction could uncover the neural basis whereby primates have become such successful social beings in the animal kingdom.