Despite empathy’s importance for promoting social interactions, neuroimaging research has largely overlooked empathy during social experiences. Here, we examined neural activity during empathy for social exclusion and assessed how empathy-related neural processes might relate to subsequent prosocial behavior toward the excluded victim. During an fMRI scan, participants observed one person being excluded by two others, and afterwards sent emails to each of these ‘people.’ Later, a group of raters assessed how prosocial (e.g., helpful, comforting) the emails were. Observing exclusion (vs. inclusion) activated regions associated with mentalizing (dorsomedial prefrontal cortex, medial prefrontal cortex, precuneus), and highly empathic individuals activated both mentalizing regions and social pain-related regions (anterior insula, dorsal anterior cingulate cortex). Additionally, the empathy-related activity in the anterior insula and medial prefrontal cortex was associated with later prosocial behavior toward the victim, and exploratory mediation analyses indicated that medial prefrontal cortex activity, in particular, may support the link between trait empathy and prosocial behavior. Overall, findings suggest that empathy-related neural responses to social experiences may promote spontaneous prosocial treatment of those in need.