OBJECTIVE Primary aldosteronism is one of the most frequent causes of secondary arterial hypertension, and whether primary aldosteronism is associated with masked hypertension is unknown. METHODS We describe a 64-year-old man with a history of hypothyroidism, recurring hypokalaemia, and normal home and office blood pressure values. Ambulatory blood pressure monitoring revealed masked hypertension with strikingly high systolic blood pressure variability and typical hypertension-mediated organ damage. RESULTS The patient required gradual escalation of antihypertensive medication to four drugs. During the diagnostic process we identified primary aldosteronism, cobalamin deficiency, severe obstructive sleep apnoea, and low baroreflex sensitivity (1.63 ms/mmHg). Following unilateral adrenalectomy, cobalamin supplementation and continuous positive airway pressure, we observed a spectacular improvement in the patient's blood pressure control, baroreflex sensitivity (4.82 ms/mmHg) and quality of life. CONCLUSIONS We report an unusual case of both masked arterial hypertension and primary aldosteronism. Elevated blood pressure values were masked in home and office measurements by coexisting hypotension which resulted most probably from deteriorated baroreflex sensitivity. Baroreflex sensitivity increased following treatment, including unilateral adrenalectomy. Hypertension can be masked by coexisting baroreceptor dysfunction which may derive from structural but also functional reversible changes.