OBJECTIVES: We investigated the impact of the COVID-19 pandemic on cancer care in a tertiary hospital in Korea without specific lockdown measures.METHODS: A retrospective cohort of cancer patients from one of the largest tertiary hospitals in Korea was used to compare healthcare utilization in different settings (outpatient cancer clinic, the emergency department [ED], and admissions to the hematology/oncology ward) between January 1 and December 31, 2020 and the same time period in 2019. The percent changes in healthcare utilization between the 2 periods were calculated.RESULTS: A total of 448,833 cases from the outpatient cohort, 26,781 cases from the ED cohort, and 14,513 cases from the admission cohort were reviewed for 2019 and 2020. The total number of ED visit cases significantly decreased from 2019 to 2020 by 18.04%, whereas the proportion of cancer patients remained stable. The reduction in ED visits was more prominent in patients with symptoms suspicious for COVID-19, high-acuity cases, and those who lived in non-capital city areas. There were no significant changes in the number of total visits, new cases in the outpatient clinic, or the total number of hospitalizations between the 2 periods.CONCLUSIONS: During the pandemic, the number of ED visits significantly decreased, while the use of the outpatient clinic and hospitalizations were not affected. Cancer patients’ ED visits decreased after the COVID-19 outbreak, suggesting the potential for collateral damage outside the hospital if patients cannot reach the ED in a timely manner.