Free flap vascular pedicle avulsion represents an extremely rare complication in reconstructive microsurgery. Very few cases have been reported in the literature, most of them identified in free flap breast reconstruction. As a result, little data is currently available on the etiology and treatment of this rare complication. Herein, we report a unique case of early venous anastomosis avulsion following free DIEP flap transfer for delayed breast reconstruction. Venous outflow was successfully restored with the use of an interposition vein graft, and the flap survived completely. In addition, the relevant literature is reviewed; and the possible causes, preventive strategies, and management options are analyzed.