A rare case of closed complete rupture of the flexor hallucis longus tendon with subsequent longitudinal tear of the flexor digitorum longus tendon is reported in a marathon runner. This is also a first case report of flexor hallucis longus transplant with cadaveric posterior tibial tendon allograft. Two minimal incisions distal and proximal to the malleolus allowed for tunneling with urethral dilators to open the tendon sheath for transplantation, avoiding the need for a large incision. Postoperatively, the patient regained active flexion at the interphalangeal joint of the left hallux. Four months after surgery, full range of motion was observed and dynamometric exam revealed 68% of the strength of the contralateral side. The patient was able to resume competitive running after the surgery and performed well in her age bracket.