Objective: To summarize the clinical, radiological characteristics, and prognosis of infectious sacroiliitis in children. Methods: A case-control study was conducted, including 12 cases of infectious sacroiliitis diagnosed in the Rheumatology and Immunology Department of the Children's Hospital affiliated with the Capital Institute of Pediatrics from June 2018 to June 2023. These cases comprised the case group. Concurrently, 28 cases of pediatric idiopathic arthritis involving the sacroiliac joint in the same department served as the control group. Basic patient information, clinical features, laboratory parameters, and clinical treatment outcomes for both groups were collected and analyzed. Independent sample t-tests and chi-squared tests were used for inter-group comparisons. Results: Among the 12 cases in the case group, there were 5 males and 7 females, with a disease duration of 0.8 (0.5, 1.2) months. Nine patients presented with fever, and 1 patient had limping gait. Human leukocyte antigen (HLA)-B27 positivity was observed in 1 case, and there was no family history of ankylosing spondylitis. In the control group of 28 cases, there were 19 males and 9 females, with a disease duration of 7.0 (3.0, 17.0) months. One patient (4%) had fever, and 14 cases (50%) exhibited limping gait. HLA-B27 positivity was found in 18 cases (64%), and 18 cases (64%) had a family history of ankylosing spondylitis. The case group had higher white blood cell count (WBC), neutrophil ratio, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) levels, as well as a higher proportion of unilateral involvement on magnetic resonance imaging and bone destruction on CT compared to the control group ((11.1±6.2)×109 vs. (7.3±2.3)×109/L, 0.64±0.10 vs. 0.55±0.12, 72 (34, 86) vs. 18 (5, 41) mm/1 h, 24.6 (10.1, 67.3) mg/L vs. 3.6 (0.8, 15.0) mg/L, 11/12 vs. 36% (10/28), 9/12 vs. 11% (3/28), t=2.90, 3.07, Z=-2.94, -3.28, χ2=10.55, 16.53, all P<0.05). Conclusions: Pediatric infectious sacroiliitis often presents as unilateral involvement with a short disease history. Elevated WBC, CRP, and ESR, as well as a high rate of bone destruction, are also common characteristics.