Purpose. For more than two years since the COVID-19 pandemic, human lives have changed, including the healthcare system. Management of acute appendicitis, the most common emergency surgical disease, has been inevitably affected. This study aimed to assess the effect of the COVID-19 pandemic on the incident rate of complicated appendicitis, management, outcome, and complication of acute appendicitis. Patients and Methods. This study was a retrospective cohort study comparing 574 patients diagnosed with acute appendicitis before the COVID-19 outbreak and 434 patients diagnosed with acute appendicitis during the COVID-19 outbreak. Patient demographic data, type of appendicitis, type of treatment, time to surgery, length of stay, cost, and complications were collected and analyzed. Results. During the COVID-19 pandemic, the number of patients diagnosed with acute appendicitis was reduced. CT scan usage for diagnosis was increased compared to pre-COVID-19. Most patients diagnosed with acute appendicitis received operative treatment in both groups. Median time to surgery was significantly longer during the COVID-19 pandemic, 11.93 hours compared to 9.62 hours pre-COVID-19,
p
-value <0.001 (relative risk 1.5, 95% CI 1.29–1.76,
p
value 0.041). The incidence of complicated appendicitis was not higher during COVID-19. Compared to pre-COVID-19, ICU admission rate, the use of a mechanical ventilator, length of stay, and cost increased in the univariate analysis but were not statistically significant in the multivariate analyses. Other treatment complications had no statistically significant difference. Conclusion. The incidence of complicated appendicitis did not increase during the COVID-19 pandemic. The operation waiting time significantly increased but did not increase the rate of treatment complications in a well-prepared hospital system.