© 2016 Elsevier Inc. Aims Perfluoroalkyl substances (PFAS) are synthetic hydrocarbons shown to preserve pancreatic islet cell viability and reduce islet cell hypoxia and apoptosis. We investigated the relationship of serum PFAS with diabetes, and whether this varied by diabetes type. Methods 6,460 individuals with and 60,439 without diabetes from the C8 Health Project, were categorized into three groups: type 1 (n = 820), type 2 (n = 4,291), or uncategorized diabetes (n = 1,349, missing data on diabetes type or diabetes based on blood sugar at study entry). Four PFAS were investigated: perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorononaoic acid (PFNA). Results PFAS levels were significantly lower in those with diabetes, and lowest in those with type 1 diabetes. In age and sex adjusted analyses, ORs (CI) for type 1, type 2, and uncategorized diabetes compared to no diabetes were 0.59 (0.54–0.64), 0.74 (0.71–0.77), 0.84 (0.78–0.90), respectively for PFHxS; 0.69 (0.65–0.74), 0.87 (0.89–0.91), 0.92 (0.88–0.97), respectively for PFOA; 0.65 (0.61–0.70), 0.86 (0.82–0.90), 0.93 (0.86–1.03), respectively for PFOS; and 0.65 (0.57–0.74), 0.94 (0.88–1.00), 0.95 (0.85–1.06), respectively for PFNA. Further adjustment for eGFR and other covariates did not eliminate these inverse associations. Conclusions PFAS levels were negatively associated with diabetes. This inverse relationship was strongest for type 1 diabetes, suggesting the relationship with serum PFAS may vary with the severity of islet cell deficiency.