Per- and polyfluoroalkyl substances (PFAS) have exceptional interfacial properties and, as such, they have been widely used since the 1950s for a range of applications, including aqueous film forming foam (AFFF). Recently there has been significant concern regarding the environmental fate and impact of PFAS. In this study we collected over 40 groundwater samples from a PFAS impacted legacy fire fighting training area in Canada. Using these samples we conducted an in-depth assessment of the relationship between PFAS and in situ microbial communities. Specifically, in situ microbial communities were characterized using 16S rRNA gene amplicon sequencing to obtain a profile of the relative abundance of most microbes in sampled aquifers. Metagenomic data were analysed in conjunction with available site data, monitoring well data and soil data. Results suggest differential transport of PFAS of differing chain length and head group which is substantiated by PFAS retardation coefficients estimated from field data. There is also evidence of PFAS degradation, in particular 6:2 FTS telomer degradation. Although PFAS constituents were not major drivers of microbial community structure the relative abundance of over one hundred individual genera were significantly associated with PFAS chemistry. For example lineages within the Oxalobacteraceae family had strong negative correlations with PFAS whilst the Desulfococcus genus has strong positive correlations. Additional correlations between PFAS and individual genera were evaluated to assess the possibility of biostimulation at low concentrations and potential inhibition at high concentrations. Results suggest a range of genera may have been stimulated at low to mid-range concentrations (e.g., Gordonia), with some genera potentially inhibited at high PFAS concentrations. Any correlations identified need to be further investigated to determine the underlying reasons for observed associations as this is an open field site with the potential for many controlling factors. Positive correlations may ultimately provide important insights related to development of biodegradation technologies for PFAS impacted sites while negative correlations further improve our understanding of the potential negative effects of PFAS on ecosystem health.