Background: The increasing prevalence of type 2 diabetes mellitus (T2DM) poses a major public health challenge throughout the world. It is a major healthcare issue among the elderly. This study was to identify the association between the health promoting behaviors and the diabetic control of type 2 diabetes mellitus (T2DM) patients. Methods: Cross sectional and descriptive research designs were used in this study. Participants were enrolled from three medical centers in northern, central and southern Taiwan during August, 2010 and June, 2011. The instruments encompassed biochemical indicators, and the preliminary developed scale of diabetes mellitus and health promotion (DMHP). Results: A total of 323 participants with T2DM were included in this study. The results showed 1) a high percentage of the participants used cigarette smoking, alcohol drinking and betel nut chewing, which were not conducive to adopting health promoting behaviors; 2) a high percentage of patients showed abnormal blood glucose, dyslipidemia, and elevated blood pressure; 3) few of the participants practiced ideally health promoting behaviors; and 4) practicing health-promoting behavior was positively associated with fasting blood glucose (FBG) and HbA1c levels. Conclusions: Patients with higher health promotion scores had better diabetic control. Less physical activity was found among those addicted to cigarette, alcohol and betel nut consumption. The findings suggest that health care providers should assess health promoting behaviors first for each diabetic patient.