The effects of an in situ chemical oxidation (ISCO) treatment aimed predominantly at remediation of chlorinated volatile organic compounds (cVOCs) and perfluoroalkyl acids (PFAAs) co-contaminants were investigated. Soil and groundwater samples were collected before and after an ISCO pilot-scale field test of a peroxone activated persulfate (OxyZone) technology. Statistically significant decreases in PFAA groundwater concentrations were observed in post-treatment samples. Reductions in PFAA aqueous phase concentrations were also supported by decreases in soil concentrations. Importantly, there was no evidence for increased aqueous PFAA concentrations due to mobilization from soil or conversion of precursors into PFAAs. As indicated by chloride data from inside and outside the treatment zone, displacement and/or dilution could not explain the observed decrease in PFAA concentration. Also, relatively constant pH values, due to using a buffered oxidant solution, did not support increased PFAA removal via soil sorption. Overall, the use of peroxone activated persulfate to treat cVOCs had no discernible negative impacts on PFAA co-contaminants at the Site. Rather, the data suggest that PFAA concentrations decreased due to ISCO treatment.