OBJECTIVE: To examine the association between prolonged in-hospital time to appendectomy (TTA) and the risk of complicated appendicitis. SUMMARY BACKGROUND DATA: Historically, acute appendicitis was treated with emergency appendectomy. More recently, practice patterns have shifted to urgent appendectomy, with acceptable in-hospital delays of up to 24 hours. However, the consequences of prolonged TTA remain poorly understood. Herein, we present the largest individual analysis to date of outcomes associated with prolonged in-hospital delay before appendectomy in children. METHODS: Data from patients who underwent appendectomy within 24 hours of hospital presentation were obtained from the American College of Surgeons Pediatric National Surgical Quality Improvement Program Procedure Targeted Appendectomy database from 2016 to 2018. Appendectomy within 16 hours of presentation was considered early, whereas those between 16 to 24 hours were defined as late. The primary outcome was operative findings of complicated appendicitis. Secondary outcomes included 30-day complications and resource utilization. RESULTS: This study consisted of 18,927 patients, with 20.6% undergoing late appendectomy. The rate of complicated appendicitis was significantly higher in the late group (Early: 26.3%, Late: 30.3%, P < 0.05). Additionally, the late group had longer operative times, increased need for postoperative percutaneous drainage, antibiotics at discharge, parenteral nutrition, and an extended hospital length of stay (P < 0.05). On multivariate analysis, late appendectomy remained a predictor of complicated disease (odds ratio 1.17 [95% confidence interval, 1.08-1.27]). CONCLUSIONS: A significant proportion of pediatric patients with acute appendicitis experience prolonged in-hospital delays before appendectomy, which are associated with modestly increased rates of complicated appendicitis. Although this does not indicate appendectomy needs to be done emergently, prolonged in-hospital TTA should be avoided whenever possible.