Atrial fibrillation (AF) is prevalent in individuals with essential hypertension (HTN). Masked hypertension occurs in up to 15% of the general population and is associated with adverse clinical outcome. The aim of the current study was to evaluate the prevalence of masked hypertension in apparently normotensive individuals with lone AF. A cross sectional analytical study performed at the Rabin Medical Center included all patients > 18 years who visited the emergency department (ED) in the years 2018–2021 with idiopathic AF, had normal blood pressure (BP) values during their ED visit and did not have a history of hypertension or current use of anti-hypertensives. Ambulatory blood pressure monitoring (ABPM) was performed in all eligible patients within 30 days from ED visit. Data collected included information from the ED visit and data extracted from the monitoring device. A total of 1258 patients were screened for eligibility, of which 40 were included in the analysis. The average age was 53.4 ± 16 years, 28 patients (70%) were males. Overall, 18 individuals (46%) had abnormal BP values according to the 2017 ACC/AHA guidelines for the diagnosis of hypertension. Of these, 12 had abnormal 24-h BP average (≥ 125/75 mmHg), one had isolated daytime abnormal average (≥ 130/80 mmHg) and 11 had isolated night time abnormal average (≥ 110/65 mmHg). Masked hypertension is prevalent in patients with lone AF without a diagnosis of HTN and performing ABPM in such individuals should be strongly considered.