Posterior tibial tendon transfer for chronic drop foot deformity can be performed to reduce a patient’s dependence on an ankle-foot orthosis. Obtaining adequate length of the posterior tibial tendon at harvest is critical for having a successful surgical outcome. The presence of an accessory navicular could limit the length of tendon available for transfer. The technique for performing a transfer of the posterior tibial tendon through the interosseous membrane in the setting of an accessory navicular is reported. Using the accessory bone to secure the transfer can lead to rapid transfer incorporation and a successful outcome. Level of Evidence: Diagnostic Level V—case report and technique guide. See Instructions for Authors for a complete description of levels of evidence.