Individuals at a clinical high risk (CHR) for psychosis have gray matter volume (GMV) abnormalities that are similar to, though less severe than, those in individuals with schizophrenia. Less GMV in schizophrenia is related to worse social cognition and social functioning, but the relationship between GMV and social functioning in CHR individuals has yet to be investigated. The aim of this study was to (1) investigate differences in GMV between healthy controls (HC) and CHR individuals, and (2) evaluate the relationship between GMV and social functioning in these two groups. Participants comprised 22 CHR and 21 HC individuals who completed a structural magnetic resonance imaging (MRI) scan as well as self-reported and interviewer-rated measures of social functioning. Processing and analysis of structural images were completed using voxel based morphometry (VBM). Results showed that the CHR group had less GMV in the left postcentral gyrus, bilateral parahippocampual gyri, and left anterior cingulate cortex. Reduced GMV in the postcentral gyrus and the anterior cingulate was related to self- reported social impairment across the whole group. This study has implications for the neurobiological basis of social dysfunction present before the onset of psychosis.