Purpose: The exercise self-efficacy scale (ESES) is largely used among diabetic patients to enhance exercise behaviour. However, the Iranian version of ESES was not available. The aim of this study was to validate ESES in this country. Method: Data were collected from 348 women who referred to a diabetes institute in Iran through convenience sampling procedure. In this cross-sectional study, exploratory factor analysis and confirmatory factor analysis was used to examine construct validity of scale. Results: Through exploratory factor analysis, 18 items of the scale converged to three factors with rotation. Construct validity was determined by confirmatory factor analysis through which modified model of self-efficacy scale with 17 items was supported and cross validated. Cronbach's alpha coefficient for the whole scale was obtained as 0.92, which indicates the reliability of the scale. Conclusion: In general the findings suggest that the ESES with some minor changes is a reliable and valid measure of exercise self-efficacy among the Iranian diabetic population. However, further studies are needed to establish stronger psychometric properties for this scale. (Contains 6 tables.)