This survey was performed to investigate the incidence of adverse reactions to radiopharmaceuticals in FY2020 in Japan. The results are based on responses to questionnaires sent to nuclear medicine centers. Replies were obtained from 1,006 centers out of 1,212 to which the questionnaire was sent. A total of 940,758 administrations of radiopharmaceuticals were reported. There were 17 cases with adverse reactions, giving an incidence of adverse reactions of 1.8 per 100,000 cases. Two cases of defective products were reported, giving an incidence of defective products of 0.2 per 100,000 cases.