To examine the association between health literacy, level of disease knowledge, and adherence behavior among patients with type 2 diabetes. A cross-sectional survey study of 1059 Mandarin- and Taiwanese-speaking patients aged 20 years or older with type 2 diabetes was conducted. The demographic profiles of the sample strata were determined by analyzing the Taiwanese National Health Insurance Database. Participants were enrolled and completed questionnaires between April and November of 2015. The patients were assessed using a self-developed questionnaire with high internal consistency (KR-20 = .84). Construct validity was supported by Confirmatory Factor Analysis. Respondents scored lowest in diet-related knowledge. Health literacy and diabetes knowledge were significantly greater when patients cared for themselves with additional caretaker assistance. Patient age, gender, and educational attainment were associated with adherence behavior. This study conducted a nation-wide survey of patients with diabetes and the results showed that respondents possessed fairly strong diabetes-specific health literacy and knowledge. However, health literacy shouldn't be assessed as an isolated concept. Instead, it should be assessed in conjunction with adherence behavior.