Background: The prevalence of diabetes is increasing. The goal of diabetes control is keeping blood sugar in ideal range which indicates the importance of self-care behaviors. Purposes: The purposes of this study were to investigate the relationship among self-efficacy, social support, and self-care behaviors, and variables significantly associated with self-care behaviors. Methods: The cross-sectional survey method was used. A total of 600 type 2 diabetes patients were recruited from outpatient Diabetes Shared Care department in a medical center in northern Taiwan. The structured questionnaires, including demographic characteristics, self-efficacy, social support, and self-care behaviors were administered. Results: The findings were as follows: (1) 53 % patients were overweight or obesity, 52.5% had other kinds of chronic diseases. (2) The average score of self-efficacy was 4.27. The average score of social support was 3.95. The average score of self-care was 4.08. (3) Patients who were aged over 65 years old, suffering over 10 years, illiterate, taking oral medication, had better self-care behaviors. Patients with graduated above senior high school and without other kinds of chronic diseases had better glucose test adherence. (4) self-efficacy and social support had positive correlation with self-care behaviors (r= .872 and .824, respectively, p＜ .001). (5) Age, body weight, treatment methods, self-efficacy and social support may explain 79.1% total amounts of variation. Conclusions/Implications for Practice: Nurses could promote patients’ ability of self-efficacy and reinforce of social support to get self-care behaviors. The results of this study could be used as a reference for clinical diabetes nursing care.