Theory of mind (ToM), the capacity to reason about others’ mental states, is central to healthy social development. Neural mechanisms supporting ToM may contribute to individual differences in children’s social cognitive behavior. Employing a false belief functional magnetic resonance imaging paradigm, we identified patterns of neural activity and connectivity elicited by ToM reasoning in school-age children ( N = 32, ages 9–13). Next, we tested relations between these neural ToM correlates and children’s everyday social cognition. Several key nodes of the neural ToM network showed greater activity when reasoning about false beliefs (ToM condition) vs non-mentalistic false content (control condition), including the bilateral temporoparietal junction (RTPJ and LTPJ), precuneus (PC) and right superior temporal sulcus. In addition, children demonstrated task-modulated changes in connectivity among these regions to support ToM relative to the control condition. ToM-related activity in the PC was negatively associated with variation in multiple aspects of children’s social cognitive behavior. Together, these findings elucidate how nodes of the ToM network act and interact to support false belief reasoning in school-age children and suggest that neural ToM mechanisms are linked to variation in everyday social cognition.