Objective: Low adherence to physical activity remains a significant barrier to achieving glycemic control in patients with diabetes. The purpose of the study was to examine the validity and reliability of the 10-item Perceived Therapeutic Efficacy Scale for Physical Activity (PTES-PA) Korean version in 108 Korean adults with diabetes at risk for metabolic syndrome. Methods: This study was part of an ongoing study of baseline data. The Korean translated PTES-PA was back-translated to ensure translation equivalency. A cross-sectional survey was used to evaluate the psychometric properties with exploratory factor analysis for validity and Cronbach’s alpha coefficient for reliability. Results: The factor analysis of construct validity identified one dimension of PTES-PA, explaining 79.4% of the total variance and providing initial evidence of validity. The internal consistency reliability for the total instrument was acceptable with a Cronbach's alpha of 0.971. There was good correlation between the PTES-PA and Self-Efficacy for Appropriate Medication Use Scale (r = 0.389; p < 0.001), indicating that these scales measure theoretically related constructs for convergent validity. As evidence of known-groups validity, there was a significant association between the PTES-PA score and glycemic control (p < 0.05), indicating that the good glycemic controlled group was more likely to have a high score of PTES-PA than the poor glycemic controlled group. Conclusion: These results support the cross-cultural applicability of the concepts underlying the PTES-PA with adequate reliability and validity. The PTES-PA may be used to examine the potential role of physical activity in enhanced glycemic control of populations with diabetes in clinical settings. *This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (grant number: 2016R1D1A1A09917287)