Perfluorooctanoic acid (PFOA), widely used in various industries and released during cooking as a PTFE precursor, poses significant environmental concerns due to its persistence and toxicity. This study investigated the degradation behavior of PFOA at the gas–liquid interface under diverse conditions. The results demonstrate that the coexistence of salts, particularly NaBr, significantly enhances PFOA degradation by promoting electron transfer reactions. Alkaline conditions (pH 9.8) and the presence of oxygen further facilitate its degradation, whereas acidic conditions hinder this process. Mechanistic analysis further confirmed that hydroxyl radicals (•OH) and hydrated electrons (eaq–) play critical roles in the observed degradation. This work provides new insights into the transformation of PFAS under diverse conditions and offers a basis for developing strategies to degrade PFOA into environmentally benign species.