Metacognitive beliefs about emotions expressed by others are crucial to social life, yet very little studied. To what extent does our confidence in emotion expression recognition depend on perceptual or other non-perceptual information? We obtained behavioral and magnetic resonance imaging measures while participants judged either the emotion in ambiguous faces or the size of two lines flanking these faces, and then rated their confidence on decision accuracy. Distinct behavioral and neural mechanisms were identified for confidence and perceptual decision in both tasks. Participants overestimated their emotion recognition (ER) accuracy, unlike visual size judgments. Whereas expression discrimination recruited several areas in the face-processing network, confidence for ER uniquely engaged the bilateral retrosplenial/posterior cingulate complex and left parahippocampal gyrus. Further, structural white matter connectivity of the former region predicted metacognitive sensitivity. These results highlight a key role for brain mechanisms integrating perception with contextual mnemonic information in the service of confidence during ER