Purpose: This purpose of this study was to develop and validate a Self-Efficacy Scale for Self-Management of Breast Cancer (SESSM-B). Methods: The SESSM-B was developed and validated as follows: Item generation, pilot study, and tests of validity and reliability. Twenty-one items were developed through evaluation by 10 experts and 13 items were finally confirmed through item analysis and factor analysis. Psychometric testing was performed with a convenience sample of 303 women with breast cancer. Data were analyzed using factor analysis, Pearson correlation coefficients, and Cronbach’s alpha. Results: Five factors evolved from the factor analysis, which explained 69.8% of the total variance. The first factor ‘coping with psycho-informational demand’ explained 17.2%, 2nd factor ‘maintenance of healthy lifestyle’ 14.5%. 3rd factor ‘management of sideeffects' 13.3%, 4th factor ‘therapeutic compliance’ 12.8%, and 5th factor ‘sexual life’ 11.9%. SESSM-B also demonstrated a concurrent validity with health-related quality of life scale, EORTC QLQ-C30 qqqamp; BR23. The internal consistency, Cronbach’s alpha, was .78, and reliability of the subscales ranged from .61 to .79. Conclusion: The results of this study suggest that the SESSM-B is an easy, reliable, and valid instrument to measure self-efficacy for self-management of breast cancer.