Aggression is a common response to provocation, albeit with considerable interindividual differences. In this fMRI study, we investigated emotional reactivity to threat as possible link between provocation and aggression, as well as the neural correlates of this relationship. We hypothesized that emotional reactivity, measured as fear potentiation (FP) of the startle response, would be negatively associated with aggressive behavior and would modulate neural activity during an aggressive interaction. In 30 healthy female participants, FP was measured as the difference between blink amplitudes while watching threatening vs neutral pictures. Participants subsequently engaged in a variant of the Taylor Aggression Paradigm (TAP), while being scanned. During the TAP, participants selected a punishment level for either a highly provoking or a nonprovoking opponent. There was no difference in aggressive behavior between participants high and low in FP. However, we found a negative correlation between FP and the neural provocation effect in several regions of a network previously associated with mentalizing including the medial prefrontal cortex, precuneus and the temporo-parietal junction. Independently of the FP variability, aggressive behavior correlated with the provocation effect on activity in the caudate nucleus. Our results indicate that during a provocative confrontation, high emotional reactivity to threat suppresses recruitment of the mentalizing network.