Free autologous tissue transfer has been used in mastectomized patients for high-quality reconstruction. Since the deep inferior epigastric perforator flap was developed, it has been considered preferable owing to reduced donor site morbidity. At our institution, anastomosis of internal mammary vessels has been top priority because of better positioning and shorter pedicle length. We publish our experiences with various technical modifications that assure internal mammary vessel anastomosis. From 2003 to 2008, 35 patients received free deep inferior epigastric perforator flap for breast reconstruction by anastomosis with internal mammary vessels. Twenty-nine reconstructions were done immediately upon mastectomy whereas six were delayed. The patterns of anastomosis between the flap pedicle and internal mammary vessel were categorized and the results were followed by flap survival and complications. These deep inferior epigastric perforator flaps were all supplied by a single pedicle artery. Twenty-five of them were drained by a single pedicle vein, and the venous anastomosis pattern was end to end to the single internal mammary vein (IMV) (type I, N = 25). However, the other nine flaps were drained by one pedicle vein anastomosed end to end to double IMV (type II, N = 2), end to end to both proximal and distal ends of single IMV (type III, N = 5), end to end and end to side to single IMV (type IV, N = 2), and end to end to single IMV without anastomosing the other (type V, N = 1). All flaps were successful, except in one patient with type I anastomosis who received vascular reexploration due to pedicle twisting. Another patient with type I anastomosis needed revision due to partial fat necrosis of the flap. No other complications were found. Various modifications of internal mammary vessel anastomosis can be used to ensure the safety of deep inferior epigastric perforator flap in breast reconstruction.