Purpose: The purpose of this study was to develop and validate a diabetes management self-efficacy scale for older adults (DMSES-O). Methods: A preliminary DMSES-O of 22 items was derived from a literature review and seven domains of self-management behaviors. Content validity was confirmed by experts in diabetes self-management education. To test the reliability and validity of the DMSES-O, data were collected from 150 older adults with type 2 diabetes. The data were analyzed using exploratory factor analysis, and Cronbach"s ? and Pearson"s correlation coefficients were calculated. Results: From the exploratory factor analysis, 17 significant items in six subscales were derived. Factors derived were named “problem solving for hypoglycemia and self-monitoring blood glucose,” “problem solving for hyperglycemia,” “coping with psychological distress and taking medication,” “reducing risks of diabetes complications,” “appropriate exercise,” and “healthy eating.” The criterion-related validity of the DMSES-O was established by its correlation with the Summary of Diabetes Self-care Activities Questionnaire. Cronbach"s ?, a measure of internal consistency, was .84 for the overall scale and ranged from .54 to .80 for the subscales. Conclusion: The DMSES-O is a reliable and valid instrument to measure selfefficacy for diabetes self-management among older adults.