In social contexts, errors have a special significance and often bear consequences for others. Thinking about others and drawing social inferences in interpersonal games engages the mentalizing system. We used neuroimaging to investigate the differences in brain activations between errors that affect only agents themselves and errors that additionally influence the payoffs of interaction partners. Activation in posterior medial frontal cortex (pMFC) and bilateral insula was increased for all errors, whereas errors that implied consequences for others specifically activated medial prefrontal cortex (mPFC), an important part of the mentalizing system. The results demonstrate that performance monitoring in social contexts involves additional processes and brain structures compared with individual performance monitoring where errors only have consequences for the person committing them. Taking into account how one’s behavior may affect others is particularly crucial for adapting behavior in interpersonal interactions and joint action.