Prions, the etiological agents in transmissible spongiform encephalopathies, exhibit remarkable resistance to most methods of inactivation that are effective against conventional pathogens. Prions are composed of pathogenic conformers of the prion protein (PrP^TSE). Some prion diseases are transmitted, in part, through environmental routes. The recalcitrance of prions to inactivation may lead to a persistent reservoir of infectivity that contributes to the environmental maintenance of epizootics. At present, few methods exist to remediate prion-contaminated lands. Here we examined the ability of peroxymonosulfate to degrade PrP^TSE as an initial step toward developing an in situ chemical oxidation process to inactivate prions. We find that peroxymonosulfate rapidly degrades PrP^TSE from two species. Transition metal-catalyzed decomposition of peroxymonosulfate to produce sulfate radicals appears to enhance degradation. We further demonstrate that exposure to peroxymonosulfate significantly reduced PrP^C-to-PrP^TSE converting ability as measured by protein misfolding cyclic amplification, used as a proxy for infectivity. Liquid chromatography-tandem mass spectrometry revealed that exposure to peroxymonosulfate results in oxidative modifications to methionine and tryptophan residues. This study indicates that peroxymonosulfate may hold promise for in situ remediation of prion-contaminated surfaces.