Objective: After the coronavirus disease 2019 (COVID-19) outbreak, there have been some changes in the way the medical system deals with suspected infectious diseases. These changes may also affect non-COVID-19 patients. Acute appendicitis is a common disease that requires emergent surgical intervention in pediatric patients, and delayed diagnosis and treatment may cause some complications. This study analyzed the impact of the COVID-19 pandemic on the incidence of complicated appendicitis in pediatric patients presenting to emergency departments in South Korea. Methods: The target group (post-COVID group) included patients aged under 15 years and diagnosed with acute appendicitis between February 23 and November 30, 2020. Patients diagnosed during the same period in 2019 were selected as the control group (pre-COVID group). The difference in the incidence of complicated appendicitis before and after the COVID-19 outbreak was investigated, and the association with various variables was analyzed using the odds ratios and 95% confidence intervals. Results: The study enrolled a total of 94 patients: 54 in the pre-COVID group and 40 in the post-COVID group. There was no statistically significant variation in the incidence of complicated appendicitis (31.5% vs 35.0%, P=0.723) between the groups. In-hospital time was longer in the post-COVID group (7 hours vs. 10.5 hours, P=0.014), but pre-hospital time showed no significant difference (16 hours vs. 22 hours, P=0.768). In the multivariable logistic regression analysis, pre-hospital time (odds ratio [OR], 1.08; P=0.004), erythrocyte sedimentation rate (OR, 33.24; P<0.001), and the presence of fever (OR, 21.11, P=0.002) showed a significant correlation. Conclusion Post the COVID-19 pandemic outbreak, there was no difference in the incidence of pediatric complicated appendicitis in South Korea.