Background: This study aimed to estimate the prevalence and trends of participation in physical activity (PA) in Korean adults. Methods: The Korea National Health and Nutrition Examination Survey (KNHANES; 2009–2013) and the Korea Community Health Survey (KCHS; 2009–2013) were used to estimate the prevalence of PA. Age standardization was performed using population projections for Korea in 2005 as a standard population. Trends of the prevalence from 2009 to 2013 were assessed by joinpoint regression analysis. Results: The age-standardized prevalence for achieving the recommended level of PA was 63.0% in KNHANES and 64.5% in KCHS for men, and 53.7% in KNHANES and 56.3% in KCHS for women. Decreasing trends were observed for the prevalence of achieving the recommended level of PA in the KNHANES and KCHS; however, only the trend for women in KNHANES was statistically significant. Conclusions: Approximately, 60% of adults participate in the recommended level of PA in Korea. The survey design and characteristics should be considered when interpreting the prevalence of PA from different databases.