Perfluoroalkyl substances (PFASs) are widespread synthetic substances with various adverse health effects. A potential mechanism of toxicity for PFASs is via epigenetic changes, such as DNA methylation. In this exploratory study with school-age children exposed to PFASs through drinking water highly contaminated from firefighting foams, we aimed to investigate whether exposure to PFASs was associated with alteration in DNA methylation and epigenetic age acceleration. Sixty-three children aged 7–11 years from the Ronneby Biomarker Cohort (Sweden) were included. The children were either controls with only background exposure (n=32; perfluorooctane sulfonic acid: median 2.8 and range AQ11 1–5ng/ml) or those exposed to very high levels of PFASs (n=31; perfluorooctane sulfonic acid: median 295 and range 190–464ng/ml). These two groups were matched on sex, age, and body mass index. Genome-wide methylation of whole-blood DNA was analyzed using the Infinium MethylationEPIC BeadChip kit.