Objectives The objective of this study was to investigate changes in physical activity (PA) between January (before the COVID-19 epidemic) and April (during the COVID-19 epidemic) 2020 in community-dwelling older adults in Japan. Design Cross-sectional online survey. Setting and Subjects From April 23 to 27, 2020, an online survey was completed by 1,600 community-dwelling older adults in Japan. Methods We assessed the frailty status using the Kihon checklist, and other demographics and asked questions regarding PA at two time points: January and April 2020. We defined the total PA time (minutes) per week based on activity frequency and time. Results The study participants’ mean age, proportion of women, and prevalence of frailty were 74.0±5.6 years, 50% (n=800), and 24.3% (n=388), respectively. We found a significant decrease in total PA time in April 2020 (median interquartile range (IQR), 180 0 to 420) when compared to January 2020 (median IQR, 245 90 to 480) (P<0.001). We also performed a subgroup analysis according to the frailty category; total PA time significantly decreased in April 2020 when compared to January 2020 for all frailty categories (P<0.001). Conclusion In conclusion, due to the COVID-19 epidemic, the total PA time in April 2020 significantly decreased compared to that in January 2020 in older adults. This finding may lead to a higher incidence of disability in the near future in older people.