Whether the COVID-19 pandemic has long-lasting effects on physical activity (PA) and sedentary behavior in the vulnerable older adult population is uncertain. A total of 387 older adults (75 +/- 6 years) completed a retrospective questionnaire on time spent sitting, walking, and performing aerobic and muscle-strengthening PA before, during the first three months, and one year into the COVID-19 pandemic. Whether the participants met the aerobic and muscle-strengthening PA guidelines was then determined. Of the 387 older adults, 376 (97%) were vaccinated. The participants completed 361 +/- 426, 293 +/- 400, and 454 +/- 501 min/week of moderate-to-vigorous aerobic PA before, during the first three months, and one year into the pandemic, respectively. During the same time periods, the participants performed muscle-strengthening PA 87 +/- 157, 68 +/- 163, and 90 +/- 176 min/week, walked 2.4 +/- 1.7, 2.3 +/- 1.7, and 2.6 +/- 1.9 h/day, and sat 6.2 +/- 2.9, 7.4 +/- 3.1, and 6.1 +/- 2.9 h/day, respectively. Aerobic PA, muscle-strengthening PA, and walking time decreased, whereas sitting time increased, during the first three months of the pandemic (p < 0.05), and then returned to pre-pandemic levels after one year (p < 0.05). The percentage of participants meeting both aerobic and muscle-strengthening PA guidelines decreased during the first three months of the pandemic (48.9% to 33.5%, p < 0.001), but returned to pre-pandemic levels one year later (p < 0.001). In conclusion, the COVID-19 pandemic significantly decreased PA and increased sitting time in older adults; however, both PA and sitting time returned to pre-pandemic levels after one year.