Background and objective: This study aimed to investigate the changes and trends in various measures of physique and physical fitness in Korean adults from 2009 to 2017. Material and methods: The physique and physical fitness levels of 19,415 Korean adults aged 20-69 years were investigated using data from the Survey of National Physical Fitness conducted by the Korea Institute of Sport Science. Physical fitness variables included muscular strength (grip strength), muscular endurance (sit-up exercise), power (standing long jump), cardiovascular endurance (20-m shuttle run), and flexibility (sit and reach exercise). Differences between physique and physical fitness variables were evaluated using Pearson’s correlation coefficient. Results were expressed as an intensification factor. Results: A significant relationship was identified between physique and physical fitness variables (P 0.05), excluding power and flexibility (r = -0.003, P = 0.683). Height and weight increased in men and women in all age groups except those in the age group of 60-69 years; in this age group, a decrease in height was observed in men, and a decrease in weight was observed in both sexes. Men aged 40-49 years and women aged 20-29 years demonstrated a rapid increase in body mass index (BMI). Muscular strength decreased dramatically in both sexes from the age of 40 years. Muscular endurance increased within each age group, most significantly in men aged 60-69 years (32.01%) and women aged 50-59 years (21.0%). However, absolute muscular endurance decreased with age. Power increased significantly in men aged 60-69 years (5.61%) and women aged 20-29 years (2.60%), but decreased in men aged 40-49 years (-2.84%) and women aged 60-69 years (-1.89%). Cardiovascular endurance decreased after the age of 30 years in both sexes, with maximum decrease in men aged 40-49 years (-0.77%) and women aged 60-69 years (-9.33%). Flexibility decreased from the age of 30 years in both sexes: men aged 20-29 years (-24.25%) and women aged 30-39 years (-6.60%) showed the maximum decrease. Conclusion: Overall, the following trends were found: BMI increase is likely to occur in men in their 30s and 40s and women in their 60s; muscular strength rapidly decreases in men and women in their 40s; muscular endurance increases over time in men compared to that in women; power reinforcement exercise is necessary for both men and women in their 40s to overcome decreased power; cardiorespiratory endurance largely decreases during the 20s; and flexibility tends to decrease largely in men from the 20s to 40s. There is a correlation between physique and physical fitness in Korean adults. Moreover, the physical fitness level decreases with age. Regular exercise is recommended to improve physical fitness and prevent aging.