Effective social interactions necessary for getting affiliative and instrumental needs met require the smooth integration of social skills, including verbal, non-verbal, and paralinguistic behaviors. Schizophrenia is characterized by prominent impairments in social and role functioning, and research on younger individuals with the illness has shown that social skills deficits are both common and distinguish the disease from other psychiatric disorders. However, less research has focused on diagnostic differences and correlates of social skills in older persons with schizophrenia. To address this question, we examined diagnostic and gender differences in social skills in a community-dwelling sample of 183 people older than age 50 with severe mental illness, and the relationships between social skills and neurocognitive functioning, symptoms, and social contact.Individuals with schizophrenia had worse social skills than those with bipolar disorder or major depression, with people with schizoaffective disorder in between. Social contact and cognitive functioning, especially executive functions and verbal fluency, were strongly predictive of social skills in people with schizophrenia and schizoaffective disorder, but not those with mood disorder. Other than blunted affect, symptoms were not predictive of social skills in either the schizophrenia spectrum or the mood disorder group. Older age was associated with worse social skills in both groups, whereas female gender was related to better skills in the mood disorder group, but not the schizophrenia group. The findings suggest that poor social skills, which are related to the cognitive impairment associated with the illness, are a fundamental feature of schizophrenia that persists from the onset of the illness into older age.