The capacity to engage and communicate in a social world is one of the defining characteristics of the human species. While the network of regions that compose the social brain have been the subject of extensive research in adults, there are limited techniques available for monitoring young infants. This study used near infrared spectroscopy to investigate functional activation in the social brain network of 36 five-month-old infants. We measured the hemodynamic responses to visually presented stimuli in the temporal lobes. A significant increase in oxyhemoglobin was localized to 2 posterior temporal sites bilaterally, indicating that these areas are involved in the social brain network in young infants.