BACKGROUND: Atrial fibrillation (AF), which contributes to an increased risk of stroke, frequently remains undetected, suggesting an unmet need for easier and more reliable AF screening. The reports on screening AF using an Omron blood pressure (BP) monitor with an irregular heartbeat (IHB) detector show inconsistent results, so the aim of this study was to develop a novel algorithm to accurately diagnose AF with 3 BP measurements using an Omron automated BP monitor with IHB detector.Methods and Results:In total, 303 general cardiac patients were included. Real-time single-lead ECG revealed AF in 44 patients. BP measurement was performed 3 times per patient using the Omron BP monitor HEM-907, and the number of IHBs detected was recorded. Based on these data, we developed the following algorithm: ≥1 IHB is detected during at least 2 of 3 BP measurements and the maximum number of IHBs detected is ≥2. Using this algorithm, we achieved a sensitivity of 95.5% and specificity of 96.5%, for diagnosing AF. CONCLUSIONS: The novel algorithm with 3 BP measurements using the Omron automated BP monitor with IHB detector showed high sensitivity and specificity for diagnosing AF in general cardiac patients.