Background: The deep inferior epigastric artery (DIEA) typically runs superficial to the transversalis fascia, enters the rectus sheath at the arcuate line, and terminates in a variable branching pattern while supplying musculocutaneous perforators to the lower abdominal wall. Detailed knowledge of the DIEA and its perforator anatomy is essential for harvesting a viable DIEA perforator flap, the most common free flap used in autologous breast reconstruction. This case describes a previously unreported DIEA perforator variation. Case: A 55-year-old woman underwent delayed unilateral DIEA perforator flap breast reconstruction. She had no history of previous abdominal surgery. Pre-operative CT angiography and intra-operative findings demonstrated a dominant paraumbilical, medial-row perforator arborising extensively within the planned flap. The subfascial perforator followed a medial paramuscular course, pierced the posteromedial rectus sheath, traversed the peritoneal cavity for 5 cm, and then re-entered the rectus sheath to continue caudally to join the medial branch of the DIEA pedicle. The flap was elevated on this perforator and the posterior rectus sheath was repaired primarily. Discussion: Cadaveric, case-based, and angiographic studies have identified peritoneo-cutaneous perforators to the abdominal wall. These perforators arise from intra-abdominal vessels rather than the DIEA. Other reports describe the main DIEA pedicle piercing the rectus sheath superior to the arcuate line. To our knowledge, this is the first description of a transperitoneal perforator arising from the DIEA. Conclusion: Although exceedingly rare, surgeons should be aware of this perforator variation when planning and executing a DIEA perforator flap.