UV/Fe²⁺/peracetic acid (PAA) as an efficient and novel advanced oxidation system was reported to produce reactive species (i.e., hydroxyl radicals (˙OH) and organic radicals) for triclosan (TCS) degradation, which is a representative of pharmaceutical and personal care products (PPCPs). The effects of initial pH, PAA dosage and common water matrix on TCS degradation were investigated. The results indicated that 1 μmol L⁻¹ TCS was completely removed within 10 min at an optimum initial pH of 3.5, Fe²⁺ dosage of 10 μmol L⁻¹, PAA dosage of 1 mmol L⁻¹ and temperature of 25 °C. The presence of HCO₃⁻ and natural organic matter (NOM) showed obviously negative effect on TCS degradation, while NO₃⁻ strongly promoted the destruction of TCS. According to the detected nine reaction products, the probable degradation pathways of TCS by UV/Fe²⁺/PAA were proposed including ether bond cleavage, hydroxylation, dechlorination, dechlorination–hydroxylation and dehydrogenation.