BACKGROUND The association between body mass index (BMI) and recurrence of anorectal abscess remains controversial. This study investigated the exact relationship between BMI and anorectal abscess recurrence or anal fistula formation following initial surgery. MATERIAL AND METHODS This was a retrospective registry-based study conducted at the First Affiliated Hospital of Guizhou University of Chinese Medicine. Patients treated for anorectal abscess from 01/2015 to 03/2016 were included. Clinical data and time to recurrence were recorded. The Cox regression model was used to estimate the association between BMI and recurrence. RESULTS A total of 790 patients were operated on during the study period. The average age of the participants was 38.3±11.6 years, and 83.2% were male. Median follow-up was 27 (range, 1-38) months. Compared with the low BMI (range, 15.7-22.8 kg/m²) patients, the high BMI (range, 26.0-40.6 kg/m²) patients showed higher risk of recurrence (HR=1.75, 95% CI: 1.15-2.67). In the non-adjusted model, high BMI was found to be positively correlated with recurrence (HR=1.62, 95% CI: 1.10-2.40, P=0.02), and a stronger association was found in the fully adjusted model (HR=1.75, 95% CI: 1.15-2.67, P=0.01). BMI was also used as a continuous variable for sensitivity analysis, and a similar trend was observed (P=0.01 for trend). CONCLUSIONS Elevated BMI is an independent risk factor of anorectal abscess recurrence and for increased risk of abscess recurrence or anal fistula formation.