Backgrounds. Fusion of the left and right inferior pulmonary veins (PV) (confluent inferior PV, CIPV) is a rare variation. Using intracardiac echocardiography (ICE) from the left atrium (LA), we measured the posterior wall thickness (PWT) of CIPV adjacent to the esophagus and compared it with LA posterior wall thickness (LAPWT) in non-CIPV cases. Methods. Of the consecutive 986 patients undergoing atrial fibrillation (AF) ablation from July 2020 to June 2022, seven (0.7%) had CIPV with a common trunk connecting to the LA diagnosed by 3-dimentinal contrast-enhanced computed tomography. Twenty-five AF patients without CIPV served as control. ICE was done from LA to measure PWT of CIPV and LAPWT of non-CIPV cases at the level of the left inferior PV. For ablation in CIPV patients, each superior PV was individually isolated, and BOX isolation of CIPV without ablating CIPV posterior wall was added. Results. CIPV PWT was 0.7±0.1 mm, while LAPWT of non-CIPV was 2.0±0.4 mm (P<0.001). In CIPV group, the upper and lower portions of CIPV were both apart from the esophagus (mean distances, 6.7±3.4 mm and 7.9±2.7 mm, respectively). Individual superior PV isolation and BOX CIPV isolation resulted in complete isolation of all PVs. There were no complications. All CIPV patients but one remained free from AF recurrence for 376±52 days. Conclusions. Although CIPV frequency is low (0.7%), CIPV PWT is very thin and a special care is needed in ablation. The present ablation strategy is effective for complete PV isolation with a less risk of the esophageal injury.