Specific inter-ictal personality characteristics in epilepsy, sometimes referred to as “Waxman–Geschwind Syndrome”, have been recognized for centuries and extensively described. Despite the persevering clinical impression that patients with mesial temporal lobe epilepsies (MTLE) suffer from problems in communication and interpersonal relations, uncertainties and controversies remain as to the precise origin of these psychosocial difficulties. Here, we investigated social–cognitive and decision-making abilities by using a set of tasks that combine behavioral and psychological measures of social and emotional variables to answer the question of whether patients with MTLE are specifically impaired in social cognition compared to both an epilepsy group and a healthy control group. MTLE patients, an epilepsy control group (extra-MTLE; patients with epilepsy, not originating within the frontal or mesial temporal lobe) and healthy controls (HC) were assessed according to their general cognitive status as well as with our social cognition battery, which included tests of basic processes of social cognition, theory of mind, decision making, and various aspects of psychopathology and quality of life. MTLE patients were significantly impaired compared to HC on most measures of the social cognition battery. MTLE patients were predominantly impaired in general emotion recognition compared to extra-MTLE patients. Performance in the epilepsy control group, although not significantly differing from performance in either the MTLE or the healthy control group, lay between these two groups. MTLE can be considered a significant risk factor for the development of deficits in social cognition beyond weaknesses that might be associated with epilepsy as a stigmatized chronic neurological disorder. The presence of deficits in social cognition may explain various behavioural symptoms that have historically driven concepts such as “epileptic personality” or “inter-ictal personality disorder” and may indicate new routes for therapeutic interventions.