Endoscopic flexor hallucis longus (FHL) tendon transfer is a minimally invasive surgical technique that shows promise for treating chronic Achilles tendon ruptures and tendinopathies. The procedure involves transferring the FHL tendon to the plantar foot for the calcaneus. Studies have demonstrated positive outcomes with improved American Orthopedic Foot and Ankle Society scores and patient-reported results along with low complication rates. However, for optimal results in highly active individuals, simultaneous reconstruction of the gastrocnemius-soleus complex may be necessary, particularly if significant elongation is present. This study provides a detailed surgical technique for this procedure.