OBJECTIVE: The aim of this study was to assess the reliability and validity of an evaluation scale for self-management behavior related to physical activity of type 2 diabetic patients (ES-SMBPA-2D). RESEARCH DESIGN AND METHODS: Outpatients with type 2 diabetes (n = 146) completed a self-administered questionnaire supported by a semistructured interview based on a literature review. The content, factor, and concurrent validity and internal consistency and reproducibility of the scale were analyzed. Pearson's correlation coefficients for the ES-SMBPA-2D and International Physical Activity Questionnaire (IPAQ) subscale scores were calculated to evaluate the concurrent validity. RESULTS: The ES-SMBPA-2D was divided into two parts, the first dealing with self-management behavior to enhance physical activity in daily life and the second with behavior to maintain the level of physical activity. Factor analysis showed that the first part comprised four factors and the second five. The ES-SMBPA-2D correlated with the IPAQ subscales. Cronbach's alpha coefficient was between 0.56 and 0.90, and the intraclass test-retest correlation coefficient of the subscales was between 0.60 and 0.88. CONCLUSIONS: The ES-SMBPA-2D is reasonably reliable and valid and is expected to prove useful for the assessment of patients' self-management behavior and for individualized instruction.