BACKGROUND: The influence of body mass index on perioperative complications of hiatal hernia surgery is controversial in the surgical literature. AIMS: The aim of this study was to evaluate the influence of body mass index on perioperative complications and associated risk factors for its occurrence. METHODS: Two groups were compared on the basis of body mass index: group A with body mass index <32 kg/m2 and group B with body mass index ³32 kg/m2. A multivariate analysis was carried out to identify independent predictors for complications. Complications were classified based on the Clavien-Dindo score. RESULTS: A total of 49 patients were included in this study, with 30 in group A and 19 in group B. The groups were compared based on factors, such as age, Charlson Comorbidity Index, surgical techniques used, type and location of hiatal hernia, and length of stay. Findings showed that 70% of patients had complex hiatal hernia. In addition, 14 complications also occurred: 7 pleuropulmonary and 7 requiring reoperation. From the seven reoperated, there were three recurrences, two gastrointestinal fistulas, one diaphragmatic hernia, and one incisional hernia. Complications were similar in both the groups, with type IV hiatal hernia being the only independent predictor. CONCLUSIONS: Body mass index does not affect perioperative complications in anti-reflux surgery and type IV hiatal hernia is an independent predictor of its occurrence.