Free tissue transfer has become popularized for post-mastectomy autologous breast reconstruction, particularly with the abdominal wall donor site. However, in the setting of previous autologous breast reconstruction, options for later contralateral reconstruction are limited. We present a case of breast reconstruction with a free deep inferior epigastric artery perforator (DIEP) flap, which was split from the initially reconstructed breast and shared to reconstruct the opposite breast after the occurrence of a metachronous contralateral second primary breast cancer. There were no operative complications, no flap-related complications, and at two years follow-up, the patient subjectively described bilateral soft and supple breasts, which were symmetrical in a bra, and with which she has reported high satisfaction. An account of the "split DIEP flap" is provided, highlighting the planning, technique, and vascular rationale. The technique comprises partition of a previously transferred DIEP flap breast reconstruction into two parts based on preoperative computed tomographic angiography, performed to guide surgical planning in avoiding pedicle damage and identifying the portion of the flap to island. The split DIEP flap for staged bilateral autologous breast reconstruction offers two soft-tissue flaps for the price of one donor site, offering new possibilities in breast reconstruction and the broader field of tissue transplantation.