Background and ObjectivesTo validate and analyze the results of intralesional photodynamic therapy in the treatment of complex anal fistula.Study Design/Materials and MethodsThis prospective multicentric observational study enrolled patients treated for complex anal fistula who underwent intralesional photodynamic therapy (i‐PDT). The included patients were treated from January 2016 to December 2018 with a minimum follow‐up of 1 year to evaluate recurrence, continence and postoperative morbidity. Intralesional 5‐aminolevulinic acid (ALA) gel (2%) was injected directly into the fistula. The internal and external orifices were closed. After an incubation period of 2 hours, the fistula was irradiated using an optical fiber connected to a red laser (Multidiode 630 PDT) operating at 1 W/cm for 3 minutes (180 J).ResultsIn total, 49 patients were included (61.2% male). The mean age was 48 years, and the mean duration of fistula was 13 months. Of the fistulas included, 75.5% were medium transphincteric, and 24.5% were high transphincteric. The median fistula length was 4 ± 1,14 cm (range: 3–5). A total of 41 patients (83.7%) had a previous history of fistula surgery. Preoperatively, some degree of anal incontinence was found in 5 patients (10.2%). No center reported any other procedure‐related complications intraoperatively. Phototoxicity was found in one patient. In the first 48 hours after the procedure, fever was reported in 2 patients (4%). At the end of follow‐up, total healing was observed in 32/49 patients (65.3%). No patient reported new incontinence postoperatively.Conclusioni‐PDT could be considered a good choice in patients with complex anal fistulas to avoid surgery and its complications. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.