Prolific use, mobility, and chemical stability make assessing the fate and transport of per- and polyfluoroalkyl substances (PFAS) particularly complex. New analytical techniques will be required to distinguish between PFAS of different origins and to trace their transport through natural systems. This study assesses the stable carbon (δ13C) and sulfur (δ34S) isotopic signatures of PFAS from different sources. Bulk elemental analyzer-isotope ratio mass spectrometry and compound-specific gas chromatograph-isotope ratio mass spectrometry (GC-IRMS) analytical methods were used to measure the δ13C and δ34S values of multiple PFAS compounds from various vendors and production lot numbers. PFAS originating from different vendors with different lot numbers and different PFAS species showed distinct δ13C isotopic values over a wide range of δ13C values (−52.8‰ to −26.9‰). Results indicate that GC-IRMS techniques could be utilized to determine the δ13C composition of PFAS present at concentrations typical of environmental samples. Coupling stable isotopic data with co-contaminant or isomer data could help to further differentiate PFAS sources. The development of new environmental forensics tools such as these will be necessary to elucidate the PFAS source and transport in natural systems and may inform remediation and pollution prevention protocols for PFAS.