Background: The accurate diagnosis of complicated appendicitis has been improved by using various diagnostic modalities. However, no preoperative diagnostic method could completely confirm the results. Therefore, preoperative diagnosis of complicated appendicitis to have the right management is still a huge challenge. Objectives: The aim of this study was to evaluate the diagnostic value of ultrasound combined with pediatric appendicitis score for differentiation between acute uncomplicated appendicitis and acute complicated appendicitis in a pediatric population. Methods: We prospectively evaluated 120 pediatric patients who underwent surgery for acute appendicitis from November 2017 to June 2019. Pediatric appendicitis score (PAS) was calculated and ultrasound (US) was performed before surgery. The histopathology of phlegmonous appendicitis corresponds to uncomplicated appendicitis (AUA), while gangrenous appendicitis and perforation are classified as complicated appendicitis (ACA). Results: Histopathologically, the results provided a diagnosis of acute appendicitis including 86 (71.7%) patients with AUA and 34 (28.3%) children with ACA. US findings showed a sensitivity of 23.5%, the specificity of 95.4%, PPV of 66.7%, NPV of 75.9%, and an accuracy of 75%. PAS of 8 was found to be the most appropriate cutoff point compatible with ACA; it resulted in a sensitivity of 76.5% and a specificity of 84.1%. Combining ultrasound with a pediatric appendicitis score resulted in a higher specificity to distinguish complicated from uncomplicated appendicitis when compared with ultrasound or PAS solely. Conclusions: the US is highly specific but nonsensitive for detecting complicated pediatric appendicitis. Combining ultrasound with pediatric appendicitis is a very good concept to distinguish complicated from uncomplicated appendicitis in a pediatric population.