Objective: This study examined the impact of Japan’s state of emergency on trends in diabetes care during the coronavirus disease 2019 (COVID-19) pandemic. Design: A descriptive and retrospective study. Setting: Showa University Hospital, Japan. Participants: Patients with diabetes who received medical treatment from 2018 to 2020. Determinants of interest: Number of patients with diabetes visiting the hospital per week. To examine the impact of the Japan’s state of emergency, the number hospital visiting by patients with diabetes was summarized from 28 weeks of data, from calendar week 8 to week 35, for each year. Results: Compared with the mean of 2018 and 2019, no significant difference was found between the three periods (before, during, and after the state of emergency). However, the numbers of patients from both inside and outside Tokyo increased at 7 weeks after the state of emergency was lifted. Conclusions: A significant increase in the numbers of patients with diabetes was seen compared with the same period in 2018 and 2019, suggesting that the state of emergency may have hindered diabetes care. Therefore, patients with diabetes should be followed up continuous of diabetes care while keeping a close eye on measures.