We evaluated the prevalence, awareness, treatment and control of hypertension in Korean adults with diagnosed diabetes using nationally representative data. Among subjects aged ≥30 years who participated in the Fourth Korea National Health and Nutrition Examination Survey in 2007 and 2008, a total of 745 subjects (336 men and 409 women) with a previous diagnosis of diabetes mellitus were analyzed. The prevalence of hypertension in adults with diagnosed diabetes was 55.5%. The rates of awareness, treatment and control were 88.0, 94.2, and 30.8%, respectively. Compared with the general population, the prevalence of hypertension in adults with diagnosed diabetes was higher in all age groups in both genders. Factors independently associated with a high prevalence of hypertension included being male, increasing age, single, <9 years of education, the presence of chronic kidney disease risk, hypercholesterolemia (≥240 mg dl(-1)) and high body mass index (≥25 kg m(-2)). Regular medical screening was positively associated with hypertension control, whereas a high triglyceride level (≥150 mg dl(-1)) was inversely associated. A high prevalence and a low control rate of hypertension in adults with diagnosed diabetes suggest that stringent efforts are needed to control blood pressure in diabetic patients.