BACKGROUND: Exposure to per-and polyfluoroalkyl substances (PFAS), a prevalent class of persistent pollutants, may increase the risk of type 2 diabetes. OBJECTIVE: We examined associations between PFAS exposure and glucose metabolism in youth. METHODS: Overweight/obese adolescents from the Study of Latino Adolescents at Risk of Type 2 Diabetes (SOLAR; n = 310) participated in annual visits for an average of 3:3 ± 2:9 y. Generalizability of findings were tested in young adults from the Southern California Children’s Health Study (CHS; n = 135) who participated in a clinical visit with a similar protocol. At each visit, oral glucose tolerance tests were performed to estimate glucose metabolism and b-cell function via the insulinogenic index. Four PFAS were measured at baseline using liquid chromatography–high-resolution mass spectrometry; high levels were defined as concentrations >66th percentile. RESULTS: In females from the SOLAR, high perfluorohexane sulfonate (PFHxS) levels (≥2:0 ng=mL) were associated with the development of dysre-gulated glucose metabolism beginning in late puberty. The magnitude of these associations increased postpuberty and persisted through 18 years of age. For example, postpuberty, females with high PFHxS levels had 25-mg=dL higher 60-min glucose (95% CI: 12, 39 mg=dL; p < 0:0001), 15-mg=dL higher 2-h glucose (95% CI: 1, 28 mg=dL; p = 0:04), and 25% lower b-cell function (p = 0:02) compared with females with low levels. Results were largely consistent in the CHS, where females with elevated PFHxS levels had 26-mg=dL higher 60-min glucose (95% CI: 6:0, 46 mg=dL; p = 0:01) and 19-mg=dL higher 2-h glucose, which did not meet statistical significance (95% CI: –1, 39 mg=dL; p = 0:08). In males, no consistent associations between PFHxS and glucose metabolism were observed. No consistent associations were observed for other PFAS and glucose metabolism. DISCUSSION: Youth exposure to PFHxS was associated with dysregulated glucose metabolism in females, which may be due to changes in b-cell func-tion. These associations appeared during puberty and were most pronounced postpuberty. https://doi.org/10.1289/EHP9200.