Surgical site infection (SSI) remains a common complication following orthognathic surgery, with no consensus on optimal antibiotic prophylaxis and a lack of comprehensive risk factors. This study aims to determine the incidence of SSI after orthognathic surgery and identify independent risk factors. We conducted a retrospective cohort study of 736 procedures performed in our department between January 2019 and January 2024. Demographic data, comorbidities, data on surgical procedure, and antibiotic regimens were extracted from patients' records. SSI was defined as any documented infection occurred within 12 months postoperatively. Correlations between SSI and suggested risk factors were assessed using univariable and multivariable logistic regression. Among 736 procedures performed in 699 patients, 37 (5.0 %) SSI occurred. Multivariable analysis showed that extended postoperative antibiotics reduced SSI odds by 82 % (adjusted OR = 0.18; 95 % CI [0.07-0.45]; p < 0.001). Bilateral sagittal split osteotomy (BSSO) performed alone increased SSI risk threefold (adjusted OR = 2.64; 95 % CI [1.25-5.59]; p = 0.011). Outpatient procedures were significantly associated with a lower risk of SSI (adjusted OR = 0.21; 95 % CI [0.05-0.91]; p = 0.038). Tailored postoperative antibiotic prophylaxis is pivotal in reducing SSI after orthognathic surgery.