Purpose: Many methods have been used to treat complex fistulas, but no single technique has been considered standard. Damage to the sphincter may sometimes be unavoidable, and incontinence may be an important cause of morbidity. This study aimed to validate the results of transanal opening of the intersphincteric space (TROPIS), as a technique that avoids damaging the anal sphincter, in patients with complex fistula in ano. Methods: A prospective study was conducted among 35 consecutive patients with complex fistula in ano. After a preoperative magnetic resonance fistulogram, TROPIS was performed in all patients. The St. Mark’s incontinence score was assessed preoperatively and postoperatively at 3 months. Results: The tracts were intersphincteric in 16 patients, transsphincteric in 10, extrasphincteric in 2, and horseshoe in 3. Four patients had recurrent tracts (3 transsphincteric and 1 intersphincteric). A defined follow-up schedule was used. Curettage was done if postoperative pus drainage from the wound was noted. The fistula healed in 29 patients (82.89%) following TROPIS. The remaining 6 patients received curettage, with healing in 3 (overall healing rate, 91.4%). Patients who received curettage were followed for 3 months, and the outcome was labeled as healed or failed. The mean preoperative incontinence score was 0. One patient developed incontinence to gas postoperatively in week 2, but there was no significant change in the scores at 3 months postoperatively. The mean postoperative incontinence score was 0.02. Conclusion TROPIS is an effective method for the treatment of complex fistula in ano, with minimal risk for incontinence.