Comprehension of other persons' mental states is one of the representative cognitive functions involved in social situations. It has been suggested that this function sometimes recruits emotional processes. The present fMRI study examined the neural mechanisms associated with understanding others' mental states, and the conditions that determine the recruitment of the emotional processes. The false belief paradigm, a traditional behavioral paradigm to investigate comprehension of others, was applied to an event-related fMRI analysis, allowing for the extraction of brain activity time-locked to successful understanding of others' mental states. Prominent brain activity was observed in multiple cortical regions including the medial prefrontal cortex, temporo-parietal junction, precuneus, and temporal pole. Then, correlational analyses were performed between the activations and individuals' scores of neuroticism, a personality trait that reflects emotional instability in daily life. It was revealed that the neuroticism scores were positively correlated with the activity in the temporal pole region, but not in the other regions. These results suggest that the emotional processes implemented in the temporal pole are recruited during successful understanding of other persons' mental states, and that the recruitment may be modulated by an emotional personality trait of individual subjects.