AbstractThis paper describes the development of the Glasgow Social Self‐Efficacy Scale (GSSES) and reports preliminary details of its psychometric properties.The scale was found to have a test–retest reliability correlation coefficient of 0.90 in a sample of participants with intellectual disability. This represents strong test–retest reliability. Cronbach's α for internal reliability of GSSES was 0.78 for the 38 participants with intellectual disability and 0.90 for the 19 participants in the non‐disabled group, representing acceptable internal reliability.Significant but low concurrent validity (r = 0.42) was found for non‐disabled participants between the GSSES and a previous measure of social self‐efficacy. Although both communication skill and scores on the GSSES were associated with depression, they were not significantly correlated with each other. This suggests that the belief of a person with an intellectual disability in their social ability is distinct from their social ability as rated by others and provides support for the construct validity of social self‐efficacy in this client group.The results of these tests of reliability and validity suggest the GSSES is a useful addition to cognitive measures in people with intellectual disability. Given the small sample size, verification of its psychometric properties in larger scale studies would be beneficial. Copyright © 2004 John Wiley & Sons, Ltd.