Social support and self-efficacy, that was defined as one's belief in one's capabilities to enact a certain behaviour, have a mediating effect on health outcomes and, by facilitating healthy behaviours and compliance to treatment, reduce morbidity and mortality. This pilot study aims to test whether social support and self-efficacy have a positive effect in improving health outcomes of patients with Myasthenia Gravis. 74 patients (mean age 48.1; 67.6% female) were enrolled and reported low self-efficacy and health status, but good perceived social support. Men reported better self-efficacy than women, and those living with a partner reported higher social support levels. No differences were found stratifying for disease onset, disease stage and patients' working situation. Self-efficacy and tangible support were independent predictors of mental health status. These results provide a preliminary indication that psychosocial interventions aimed to increase self-efficacy could positively mediate mental health status in myasthenic patients, especially among women.