BackgroundThis study analyzed the impact of the coronavirus disease 2019 (COVID‐19) pandemic on radiotherapy delivery in Japan using a high‐quality Japanese national database based on universal health coverage.MethodsWe performed a retrospective observational study using National Database of Health Insurance Claims and Specific Health Checkups of Japan open data focused on radiotherapy between fiscal year (FY) 2019 and FY2020 and the number of COVID‐19 cases from the Ministry of Health, Labour, and Welfare. We statistically analyzed the relationship between the number of COVID‐19 cases and the number of radiotherapy deliveries in Japan as a whole and by prefecture.ResultsThe total number of external beam radiotherapy (EBRT) fractions was 4,472,140 in FY2019 and 4,227,673 in FY2020 (−5.8%). EBRT courses were 250,395 in FY2019 and 240,329 in FY2020 (−4.0%), stereotactic radiotherapy courses were 27,619 in FY2019 and 31,786 in FY2020 (+15.1%), and single‐fraction palliative radiotherapy courses were 4124 in FY2019 and 5255 in FY2020 (+21.5%). The total number of breast and prostate hypofractionated radiotherapy (HFRT) fractions was 155,773 and 48,188 in FY2019, and 200,256 and 84,230 in FY2020 (+28.6% and +74.8%), respectively. In the Pearson correlation analysis, EBRT fractions were lower, and breast HFRT fractions were higher in prefectures with more COVID‐19 cases.ConclusionsOverall, radiotherapy delivery in Japan was relatively stable after the pandemic, with an increase in HFRT. Also, EBRT fractions decreased, and breast HFRT were more likely to be used in prefectures with more COVID‐19 cases.