Objectives: The COVID-19 pandemic has led to significant changes in daily life, including changes in physical activity levels. This study aims to examine the impact of the pandemic on sport participation and walking among Polish adults. Material and Methods: The data was collected using the National Test for Poles’ Health, a large-scale online survey. The survey was conducted before and 1 year after the pandemic onset in Poland (March 2020 and March 2021), with >300 000 participants in each year. Results: The results revealed that the percentage of respondents engaging in at least 2 h/week of sport increased by 2.3% (from 24.6% to 26.9%) (p < 0.0001) and percentage of respondents not engaging in any sport decreased by 2.5% (from 48.0% to 45.5%) (p < 0.0001). These trends were observed across different age, sex, dwelling-place, education level, and employment groups. Percentage of respondents declaring they spend >2 h/day on walking also increased, from 5.6% to 6.6% (p < 0.0001). Furthermore, a positive association was found between sport participation and walking time (p < 0.0001). Conclusions: The findings suggest a slight improvement in physical activity levels among Polish adults during the pandemic, which may be attributed to factors such as increased time available due to remote work and the prioritization of health during the crisis. Further research is needed to explore the long-term consequences of the pandemic on physical activity and public health. Int J Occup Med Environ Health. 2024;37(4):468–81