We examined the incidence and causative factors of surgical site infection (SSI) following osteosynthesis for pelvic ring injury by reviewing the data of 97 consecutive patients with pelvic ring injuries treated between 2014 and 2019. Osteosyntheses, including internal or external skeletal fixation with plates or screws, were performed based on fracture type and patient’s condition. Fractures were treated surgically, with a 36 months minimum follow-up period. Eight (8.2%) patients experienced SSI. The most common causative pathogen wasStaphylococcus aureus. Patients with SSI had significantly worse functional outcomes at 3, 6, 12, 24, and 36 months than those without. For patients with SSI, the average Merle d’Aubigné and Majeed scores at 3, 6, 12, 24, and 36 months after injury were 2.4, 4.1, 8.0, 11.0, and 11.3, and 25.5, 32.1, 47.9, 61.9, and 63.3, respectively. Patients with SSI had a higher likelihood of undergoing staged operations (50.0 vs. 13.5%,p= 0.02), more surgeries for associated injuries (6.3% vs. 2.5%,p= 0.04), higher likelihood of Morel–Lavallee lesions (50.0% vs. 5.6%, p = 0.002), higher incidence of diversional colostomy (37.5% vs. 9.0%,p= 0.05), and longer intensive care unit stay (11.1 vs. 3.9 days,p= 0.001) than those without. The contributing factors for SSI were Morel–Lavallee lesions (odds ratio [OR] 4.55, 95% confidence interval [95% CI] 3.34–50.0) and other surgeries for associated injuries (OR 2.37, 95% CI 1.07–5.28). Patients with SSI after osteosynthesis for pelvic ring injuries may have worse short-term functional outcomes.