Introduction: Previous studies of antihypertensive treatment of older patients have focused on blood pressure control, cardiovascular risk or adherence, whereas data on inappropriate antihypertensive prescriptions to older patients are scarce. Objectives: The aim of the study was to assess inappropriate antihypertensive prescriptions to older patients. Methods: An observational, prospective multicentric study was conducted to assess potentially inappropriate prescription of antihypertensive drugs, in patients aged 75 years and older with arterial hypertension (HTN), in the month prior to hospital admission, using four instruments: Beers, Screening Tool of Older Person’s Prescriptions (STOPP), Screening Tool to Alert Doctors to the Right Treatment (START) and Assessing Care of Vulnerable Elders 3 (ACOVE-3). Primary care and hospital electronic records were reviewed for HTN diagnoses, antihypertensive treatment and blood pressure readings. Results: Of 672 patients, 532 (median age 85 years, 56% female) had HTN. 21.6% received antihypertensive monotherapy, 4.7% received no hypertensive treatment, and the remainder received a combination of antihypertensive therapies. The most frequently prescribed antihypertensive drugs were diuretics (53.5%), angiotensin-converting enzyme inhibitors (ACEIs) (41%), calcium antagonists (32.2%), angiotensin receptor blockers (29.7%) and beta-blockers (29.7%). Potentially inappropriate prescription was observed in 51.3% of patients (27.8% overprescription and 35% underprescription). The most frequent inappropriately prescribed drugs were calcium antagonists (overprescribed), ACEIs and beta-blockers (underprescribed). ACEI and beta-blocker underprescriptions were independently associated with heart failure admissions [beta-blockers odds ratio (OR) 0.53, 95% confidence interval (CI) 0.39–0.71, p < 0.001; ACEIs OR 0.50, 95% CI 0.36–0.70, p < 0.001]. Conclusion: Potentially inappropriate prescription was detected in more than half of patients receiving antihypertensive treatment. Underprescription was more frequent than overprescription. ACEIs and beta-blockers were frequently underprescribed and were associated with heart failure admissions.