Thoracoacromial vein (TAv) is seldomly considered as a secondary outflow recipient option when venous congestion of deep inferior epigastric artery perforator (DIEP) flap is encountered. The purpose of this study was to present a computed tomography (CT)-based anatomy and a method of approaching TAv in performing superdrainage using superficial inferior epigastric vein (SIEV) in DIEP flap breast reconstruction. For CT-based anatomical study, 42 thoracoacromial vessels (TAV) of 21 patients who underwent DIEP flap breast reconstruction were analyzed. From November 2016 to May 2018, pectoralis major (PM) muscle splitting approach to TAv in the first intercostal space was applied to 7 patients who required superdrainage via SIEV. TAVs at mid-first intercostal space (ICS) were located 83.5 ± 9.8 mm lateral to the sternal border (H), 41.5 ± 12.9 mm below the clavicle (V), and 11.7 ± 3.2 mm deep to the outer surface of PM muscle (D). Mean oblique distances from TAV to internal mammary vessels in the 2nd and 3rd ICS were 75.7 ± 9.7 mm and 98.2 ± 10.9 mm, respectively. Seven DIEP flaps presenting intraoperative venous congestion were successfully salvaged intraoperatively with superdrainge procedure. TAvs were harvested without cutting the PM muscle in any patient. Their mean size at anastomosis was 1.61 ± 3.2 mm (range, 0.9-2.5 mm). All flaps survived without perfusion-related complications including fat necrosis. Harvest of TAv by muscle-splitting approach is an alternative option when additional venous anastomosis using SIEV is mandated for managing venous congestion of DIEP flap.