BackgroundSocial cognition has been implicated in the relationship between cognition and social functioning.AimsTo test the hypothesis that social cognition mediates the relationship between cognitive and social functioning.MethodThis was a 1-year longitudinal cohort study comparing three groups: 50 people with first-episode psychosis, 53 people with multi-episode schizophrenia and 55 people without psychiatric disorder as controls. Participants were assessed on social perception, social knowledge, interpersonal problem-solving, cognition and social functioning.ResultsThere were significant associations between social cognition, cognition and social functioning in all three groups. Deficits in social cognition were stable over time. In the first two groups, controlling for social cognition reduced the relationship between cognitive and social functioning.ConclusionsThis study provides some evidence that social cognition mediates the relationship between cognitive and social functioning.