Background. The transfer of the flexor hallucis longus (FHL) tendon is an established treatment for replacing a dysfunctional Achilles tendon. Objectives. (1) Describe a new technique for endoscopic FHL transfer for noninsertional Achilles tendinopathy and (2) describe the functional outcomes and complications after endoscopic and open FHL transfer. Materials and Method. Retrospective study of patients who underwent open or endoscopic FHL transfer between 2014 and 2016. The American Orthopaedic Foot & Ankle Society (AOFAS) ankle/hindfoot scale was used preoperatively and postoperatively to measure the functional results. Results. We included 18 endoscopic FHL transfers and 24 open FHL transfers. The mean age of endoscopic and open procedures was 47.5 years (range 25-77 years) and 61.2 years (range 43-72 years), respectively. An improvement on the average AOFAS of 52.8% (31.9 points) was observed in the endoscopy group during the follow-up from the baseline. The mean improvement in AOFAS score for the open group was 41.4% (24.5 points). Four and 7 cases reported complications in the endoscopy and open FHL transfer groups, respectively. Conclusion. While both procedures were effective in treating noninsertional Achilles tendinopathy, the described arthroscopic treatment led to a greater improvement in the AOFAS score and is slightly less prone to lasting complications. Level of Evidence: Level IV: Case series