The mobile app rating scale (MARS) is a widely used instrument for evaluating smartphone app quality. We aimed to examine the reliability and validity of the Korean version of MARS (MARS-K). Two independent raters performed the assessment using the translated 23-item questionnaire. We applied intraclass correlation coefficient analysis (ICC) to examine inter-rater reliability, Omega, and item-total correlation for internal consistency, and Pearson's r for test-retest reliability and correlation between subscales and the total score of MARS-K. Most items showed moderate to good ICC (0.447-1.000). The MARS-K showed excellent internal consistency and all subscales exceeded the acceptable level of omega. Results indicated MARS-K to be a valid and reliable instrument for evaluating disease management apps offered in the Korean app store. However, upgrades are recommended to further improve MARS-K's rating accuracy and reliability.