IMPORTANCE: Hypertension is a leading cause of cardiovascular disease. The results were previously reported of a trial of home blood pressure (BP) telemonitoring and pharmacist management intervention in which the interventions stopped after 12 months. There were significantly greater reductions in systolic BP (SBP) in the intervention group than in the usual care group at 6, 12, and 18 months (−10.7, −9.7, and −6.6 mm Hg, respectively). OBJECTIVES: To examine the durability of the intervention effect on BP through 54 months of follow-up and to compare BP measurements performed in the research clinic and in routine clinical care. DESIGN, SETTING, AND PARTICIPANTS: Follow-up of a cluster randomized clinical trial among 16 primary care clinics and 450 patients with uncontrolled hypertension in a large health system from March 2009 to November 2015. INTERVENTIONS: A home BP telemonitoring intervention with pharmacist management or usual care. MAIN OUTCOMES AND MEASURES: Change from baseline to 54 months in SBP and diastolic BP (DBP) measured as the mean of 3 measurements obtained at each research clinic visit. RESULTS: Among 450 patients, 228 (mean [SD] age, 62.0 [11.7] years; 54.8% male) were randomized to the telemonitoring intervention and 222 (mean [SD] age, 60.2 [12.2] years; 55.9% male) to usual care. Research clinic BP measurements were obtained from 326 of 450 (72.4%) study patients at the 54-month follow-up visit, including 162 (mean [SD] age, 62.0 [11.1] years; 54.9% male) randomized to the telemonitoring intervention and 164 (mean [SD] age, 60.0 [11.2] years; 57.3% male) to usual care. Routine clinical care BP measurements were obtained from 439 of 450 (97.6%) study patients at 6248 visits during the follow-up period. Based on research clinic measurements, baseline mean SBP was 148 mm Hg in both groups. In the intervention group, mean SBP at 6-, 12-, 18-, and 54-month follow-up was 126.7, 125.7, 126.9, and 130.6 mm Hg, respectively. In the usual care group, mean SBP at 6-, 12-, 18-, and 54-month follow-up was 136.9, 134.8, 133.0, and 132.6 mm Hg, respectively. The differential reduction by study group in SBP from baseline to 54 months was −2.5 mm Hg (95% CI, −6.3 to 1.2 mm Hg; P = .18). The DBP followed a similar pattern, with a differential reduction by study group from baseline to 54 months of −1.0 mm Hg (95% CI, −3.2 to 1.2 mm Hg; P = .37). The SBP and DBP results from routine clinical measurements suggested significantly lower BP in the intervention group for up to 24 months. CONCLUSIONS AND RELEVANCE: This intensive intervention had sustained effects for up to 24 months (12 months after the intervention ended). Long-term maintenance of BP control is likely to require continued monitoring and resumption of the intervention if BP increases.