Per- and polyfluoroalkyl substances (PFASs) are ubiquitous contaminants found worldwide, including in South Korea. As a result, they are frequently detected in Koreans. However, there is limited representative data and information on potential sources in Korea. Therefore, we measured the serum concentrations of ten PFASs in nationally representative samples of the Korean population (n=1874, 18-69 years) and evaluated the factors associated with their exposure. Serum PFOS, PFDA, PFOA, and PFNA were detected in nearly all participants (83.1-99.9%). However, serum PFPA, PFHxA, and PFHpA were almost undetected (<0.5% of participants). PFOS had the highest population-weighted geometric mean of 10.23ng/mL (95% CI: 9.99-10.47), which was followed by PFOA with 2.85ng/mL (95% CI: 2.73-2.97) and PFDA with 2.17ng/mL (95% CI: 2.12-2.23). PFNA, PFDA, PFHxS, PFOA, and PFOS concentrations were higher in males (p<0.001) and older adults (p<0.001). PFNA was higher in those who used wax, polish, and water-resistant materials (adjusted proportional change=1.14; 95% CI: 1.08-1.22), and those who ate cooked fish (1.16; 95% CI: 1.03-1.31) compared to those who ate nearly no fish. PFDA was higher in those who used herbicides and pesticides (1.05; 95% CI: 1.02-1.09), those who drank beverages in a plastic bag on a daily basis (1.10; 95% CI: 1.03-1.19), and those who ate raw fish (1.15; 95% CI: 1.03-1.29) or cooked fish (1.13; 95% CI: 1.05-1.23) compared to those who ate nearly no fish. PFHxS was higher in those who used traditional Korean health supplement foods (1.08; 95% CI: 1.01-1.15). PFOA was higher in those who used plastic wrap in a microwave daily or weekly (1.08; 95% CI: 1.00-1.16), and those who used disposable paper cups (1.07; 95% CI: 1.01-1.13). PFOS was lower in underweight participants (0.84; 95%CI: 0.75-0.93) compared to those who were obese, and higher in those who exercised regularly (1.08; 95% CI: 1.03-1.14) or irregularly (1.06, 95% CI: 1.01-1.12) compared to those who did not exercise. Subjects who used severely damaged Teflon appliances had lower concentrations of PFOA (0.78, 95% CI: 0.65-0.95), while regular use of Gore-Tex goods was related to higher PFNA (1.15, 95% CI: 1.03-1.28) and PFDA (1.11; 95% CI: 1.02-1.20) levels. These findings suggest that most Koreans are frequently exposed to PFASs, and that serum concentrations of PFASs vary with age, sex, and exposure factors.