Acute appendicitis is a common abdominal emergency observed in emergency departments (ED). Distinguishing between uncomplicated and complicated appendicitis is important in determining a treatment strategy. Serum soluble vascular cell adhesion molecule-1 (VCAM-1) is an inflammatory biomarker. We aimed to determine the role of VCAM-1 in predicting complicated appendicitis in children. Pediatric patients with suspected appendicitis admitted to the ED were enrolled in this prospective study. Pre-surgical serum VCAM-1 was tested in children with acute appendicitis within 72 h of symptoms (from day 1 to day 3). Serum VCAM-1 levels were further analyzed and compared between patients with and without complicated appendicitis. Among the 226 pediatric appendicitis patients, 70 had uncomplicated appendicitis, 138 had complicated appendicitis, and 18 had normal appendices. The mean serum VCAM-1 levels in patients with perforated appendicitis were higher than in those with simple appendicitis (p < 0.001). On day 1 to day 3, the mean VCAM-1 levels in patients with complicated appendicitis were all significantly higher than in those with uncomplicated appendicitis (all p < 0.001). Serum VCAM-1 levels may be helpful in differentiating uncomplicated and complicated appendicitis in children and could predict appendiceal perforation.