Objective: To evaluate the diagnostic accuracy of ultrasonography in pediatric acute appendicitis.Methods: In this cross-sectional study, 230 children aged 5-15 years with the diagnosis of acute appendicitis were studied. This study included the evaluation of demographic indices, ultrasound findings at diagnosis, and then comparing the results with the description of the patient's procedure and the pathology report of these patients. Patients who did not undergo ultrasound before surgery or their ultrasound did not include the evaluation of appendicitis or their pathologic report was not available were excluded.Results: Overall, we have included a total number of 230 children with clinical diagnosis of acute appendicitis among whom there were 121 (52.6%) girls and 109 (47.4%) boys with mean age of 11.44 ± 2.90 years. Preoperative ultrasound report showed that 51.3% were normal and 48.7% had acute appendicitis. 34.8% had normal appendix and 65.2% had a pathological diagnosis of acute appendicitis. The sensitivity and specificity of ultrasound in these children were 58% and 68%, respectively. Positive and negative predictive values were 77% and 46%, respectively. The area under curve (AUC) was 0.853 (CI 95% 0.788-0.917) indicating a test with moderate accuracy.   Conclusion: According to the obtained results, abdominal ultrasonography is of acceptable diagnostic accuracy in pediatric patients with acute appendicitis. The use of auxiliary techniques in ultrasound would increase the sensitivity and specificity in the diagnosis of acute appendicitis in children.