Complex perineal fistulas (CPFs) are among the most challenging problems in colorectal practice. Various procedures have been used to treat CPFs, with none being a panacea. Our study aimed to assess the overall success and complication rates after gracilis muscle interposition in patients with CPF. PubMed, Scopus and Google Scholar databases were systematically searched until January 2022 according to PRISMA 2020 guidelines. Studies including children <18 years or <10 patients were excluded, as well as reviews, duplicate or animal studies, studies with poor documentation (no report of success rate) and non-English text. An open-source, cross-platform software for advanced meta-analysis openMeta [Analyst]™ version 12.11.14 and Cochrane Review Manager 5.4® were used to conduct the meta-analysis of data. Twenty-five studies published between 2002 and 2021 were identified. The studies included 658 patients (409 women). Most patients had rectovaginal (50.7%) or rectourethral fistulas (33.7%). The most common causes of CPF were pelvic surgery (29.4%) and inflammatory bowel disease (25.2%). A history of radiotherapy was reported in approximately 18% of the patients. 498 (75.7%) patients with CPF achieved complete healing after gracilis muscle interposition. The weighted mean rate of success of the gracilis interposition procedure was 79.4% (95% CI 73.8%-85%, I2  = 75.3%), the weighted mean short-term complication rate was 25.7% (95% CI 18.1-33.2, I2  = 84.1%) and the weighted mean rate for 30-day reoperation was 3.6% (95% CI 1.6-5.6, I2  = 42%). The weighted mean rate of fistula recurrence was 16.7% (95% CI 11%-22.3%, I2  = 61%). The gracilis muscle interposition technique is a viable treatment option for CPF. Surgeons should be familiar with indications and techniques to offer it as an option for patients. Given the relatively infrequent use of the operation, referral rather than performance of graciloplasty is an acceptable option.