Purpose: The Health Insurance Review and Assessment Service (HIRA) in South Korea initiated a quality assessment (QA) program for blood transfusion healthcare services in 2020 to ensure patient safety and appropriate blood use. This study examines the quality of blood transfusion services since the first national QA program for blood transfusion services in Korea. Methods: We analyzed HIRA claims and QA investigation data based on inpatient medical records from all tertiary, general, and primary hospitals between October 2020 and March 2021. The target population was patients aged 18 years and older who received either total knee arthroplasty or red blood cell transfusion. The QA indicators for transfusion healthcare service consisted of four quality indicators and four monitoring indicators. Results: We analyzed the results of QA indicators for transfusion service from the medical records of 189,668 patients from 1,171hospitals and expressed indicators as proportions. The average results for evaluation indicators were as follows: transfusion checklist presence, 64.8%; irregular antibody tests, 61.8%; transfusions in which the hemoglobin levels before transfusion met the transfusion guidelines for patients undergoing total knee arthroplasty, 20.6%, and transfusions in patients undergoing total knee arthroplasty, 59.3%. The average results for monitoring indicators were as follows: transfusion management implementation in medical institutions, 56.9%; preoperative anemia management in anemia patients undergoing total knee arthroplasty, 43.9%; one-unit transfusions, 82.5%; and the transfusion index. Conclusion: The quality of blood transfusion healthcare varied and the assessment revealed that there is scope for improvement. Hospitals require more effective blood transfusion management and this can be facilitated by providing feedback on the QA results about blood transfusion healthcare services to medical institutions, and by disclosing the results to the public.