Callousness encompasses a lack of guilt, shallow affect, and deficient affiliative tendencies and relates to severe antisocial behavior. Across developmental stages, callousness is associated with abnormalities in emotional processing, including decreased physiological reactivity to emotional faces. The current study recruited an adult participant sample to investigate selective associations of callousness with deficits in behavioral performance and reduced neurophysiological response within a face-processing task. Participants higher in callousness demonstrated decreased reactivity to fearful faces across temporal components of the electrocortical response along with reduced accuracy in identifying fearful faces. Further analyses demonstrated that LPP amplitude alone was related to behavioral response and mediated the association between callousness and impaired recognition of fear faces. These findings clarify the nature of face processing deficits in relation to callousness and have implications for biologically informed interventions to reduce antisocial behavior.