The population of older adults with type 2 diabetes mellitus (T2DM) in Thailand is increasing. As this trend continues, the nursing community and public policy makers will need increasingly effective methods to improve health outcomes within this group. This study determined the significance of non-modifiable selected personal factors (age, gender, education, and duration of disease) and modifiable factors (health literacy, diabetes related numeracy, diabetes knowledge, and self-efficacy) on diabetes self-management and glycemic control in Thai older adults with T2DM. To achieve this goal it was necessary to first create a version of the Diabetes Numeracy Test (DNT) that is conceptually equivalent to the original and is appropriate for the Thai culture and age group of the study. The study was conducted in two phases. In Phase 1, multiple steps were conducted to assure the validity and reliability of the Thai DNT. After evaluating the results of that process the Thai-DNT was determined to be a suitable instrument for use in Phase 2. In Phase 2, the revised Thai-DNT was administered with the Three Levels of Health Literacy Scale, the General Diabetes Knowledge Test, the Thai version of the Diabetes Management Self-Efficacy Scale, and the Revised Summary Diabetes Self-Care Activities (SDSCA). Psychometric properties of the Thai DNT were tested. Pearson correlation coefficient was used to examine the relationships among study variables. Hierarchical multiple regression was used to predict diabetes self-management and glycemic control. A convenience sample of 170 Thai older adults with T2DM participated in the study. Participants were recruited from three primary care units and a community hospital in a suburban area, Nakhon Pathom province, Thailand. The mean age of the sample was 67.82. Most were female (61%), and a large majority had low education (80% completed at most a primary school education). Age, diabetes knowledge and self-efficacy were found to significantly predict diabetes self-management. Diabetes knowledge and duration of diabetes predicted glycemic control (A1C). Findings from this study indicate that efforts to increase diabetes knowledge and self-efficacy can help Thai older adults with their diabetes self-management behaviors and control their glycemic levels. DNT scores were low but did not account for variance in diabetes self-management and glycemic control.Nursin