Atrial fibrillation may affect blood pressure measurements. The ankle–brachial index (ABI) is a ratio of systolic blood pressure measured on the lower and upper limbs that may also be affected by arrhythmia. The purpose of the study was to investigate whether atrial fibrillation influenced ABI results. Ninety-nine patients (age 66.6±11 years, 63 males and 36 females) who underwent electrical cardioversion of atrial fibrillation were investigated. ABI measurements using the Doppler method were performed on both lower extremities before and after electrical cardioversion. Measurements were repeated three times and then averaged. The ABI using both lower limbs was lower before electrical cardioversion than after restoration to sinus rhythm (right side: 1.132 (1.065–1.210) during atrial fibrillation vs. 1.179 (1.080–1.242) in sinus rhythm, P=0.019; left side: 1.142 (1.075–1.222) during atrial fibrillation vs. 1.170 (1.098–1.255) in sinus rhythm, P=0.011). However, the upper 95% confidence interval (CI) margins for the median differences in ABI were 0.045 and 0.040 for right and left, respectively, suggesting that the observed difference was clinically insignificant. There was a significant correlation between measurements obtained before and after electrical cardioversion on both lower limbs (r=0.61, P<0.001 and r=0.67, P<0.001). The Bland–Altman plot showed good agreement between measurements performed using the Doppler method during atrial fibrillation and sinus rhythm. Study results showed that atrial fibrillation did not have a clinically important effect on ABI measurements.