Purpose: The aim of this study was to examine the validity and reliability of the Korean version of the self-efficacy for managing chronic disease 6-item scale (SECD-6-K). Methods: The English version of the Self-Efficacy for Managing Chronic Disease 6-item Scale first underwent forward and backward translation procedures. The SECD-6-K was then used to collect data from 350 adults diagnosed with chronic diseases. Content, construct, convergent, discriminant, and criterion validity were all evaluated. Reliability was assessed using Cronbach’s α. SPSS 25.0 and the data were analyzed using AMOS 26.0 software. Results: The SECD-6-K consists of six items in two domains: disease management and health behavior. The results for construct, convergent, and discriminant validity were good. Exploratory factor analysis produced eigen values between 2.27 and 3.28, with factors total explained cumulative variance of 91.1%. Confirmatory factor analysis supported goodness of fit and reliability for the modified SECD-6-K model. The criterion validity also showed significant correlation with both the Patient Health Questionnaire and 12-item Short-Form Health Survey version 2. Finally, reliability was found to be excellent. Conclusion: This study identified the high reliability and validity of SECD-6-K. The SECD-6-K is an appropriate tool for determining Korean patients’ self-efficacy in managing their chronic conditions. Therefore, this scale may be used in clinical settings as well as in educational and research settings.