An aggressive strategy to manage hypertension in a large integrated healthcare organization achieved blood pressure control in 82% of hypertensive patients, as compared with 52% nationwide. It is unknown why the remaining 18% is uncontrolled. The objective of this study was to identify characteristics associated with patients whose blood pressure remains continuously uncontrolled. This nested case-control study included 1583 continuously uncontrolled cases and 7901 matched controls. Univariate analysis revealed patients who visited their primary care provider frequently (odds ratio, 0.42; 95% confidence interval, 0.39–0.46) were adherent to antihypertensive medications (odds ratio, 0.12; 95% confidence interval, 0.10–0.14), and dispensed more medications (odds ratio, 0.86; 95% confidence interval, 0.85–0.87) were less likely to be continuously uncontrolled. Patient characteristics that were associated with continuously uncontrolled hypertension were the Patient Health Questionnaire-9 score and higher body mass index. Since patients with controlled hypertension visited their provider more often, patients with continuously uncontrolled hypertension may benefit from more interaction with their healthcare system.