Korean Society for Laboratory Medicine and the Korea Disease Prevention and Control Agency have announced guidelines for diagnosing coronavirus disease (COVID-19) in clinical laboratories in Korea. With the ongoing pandemic, we propose an update of the previous guidelines based on new scientific data. This update includes recommendations for tests that were not included in the previous guidelines, including the rapid molecular test, antigen test, antibody test, and self-collected specimens, and a revision of the previous recommendations. This update will aid clinical laboratories in performing laboratory tests for diagnosing COVID-19.