This study investigated the levels of health literacy, self-efficacy, self-management, and glycated hemoglobin (HbA1c) levels in older adults with diabetes to identify the relationships between these factors. This descriptive study consisted of 162 elderly outpatients with diabetes at the departments of endocrinology of three general hospitals in J Province, South Korea. Data were collected using a structured self-report questionnaire between October 21 and November 16, 2019. The data were analyzed using SPSS/WIN version 23.0. Health literacy was positively correlated with self-efficacy (rs=0.64, p<0.001) and self-management (rs=0.44, p<0.001) and significantly negatively correlated with HbA1c levels (rs=-.42, p<0.001). Self-efficacy showed a significantly positive correlation with self-management (rs=0.65, p<0.001) and a significantly negative correlation with HbA1c levels (rs=-.30, p<0.001). Moreover, a significant negative correlation was found between self-management and HbA1c levels (rs=-.35, p<0.001). Hence, health literacy and patient self-management levels were associated with HbA1c levels in older adults with DM. Health education for community-dwelling older adults with diabetes should consider their health literacy levels. Moreover, measures to improve self-management abilities may be needed when developing educational programs for older adults with diabetes.