This study investigated the reaction mechanisms of peracetic acid (PAA) with dihydroxybenzenes (HBs) to generate reactive species for degradation of micropollutants containing aniline(-like) structures, including 7 sulfonamide antibiotics, 17 (non-)substituted anilines, and 3 nucleobases. Three of the studied HBs significantly enhanced aniline degradation kinetics by PAA, with degrees following the order of catechol (CA) > protocatechuic acid > hydroquinone. The PAA/CA process at the optimal condition (initial pH 7, 100-μM PAA, 50-μM CA) achieved 90% removal efficiency of sulfadiazine in 40 min with minimal interference by anions (Cl-, SO42-, and HCO3-), humic acid, and real (waste)waters. Results of scavenging experiments, electron paramagnetic resonance analyses, and transformation product profiles collectively support that semiquinone radical (SQ•-), originated from oxidation of CA by PAA, dominated aniline degradation through nucleophilic addition toward the amino groups on aniline moieties, resulting in formation of C-N coupling products and detoxication of anilines. The critical role of o-SQ•- is further highlighted by the linear correlation between ln-scale observed pseudo-first-order rate constant (kobs) with the Hammett constant (σ) for sulfonamides and (non-)substituted anilines (r = -0.77). Besides, a non-radical pathway driven by singlet oxygen (1O2) made important while non-dominant contribution to aniline degradation. Overall, this work sheds light on reactive species formation during oxidation of phenolic compounds by PAA and proposes a novel strategy for selective elimination of aniline-containing contaminants in wastewater treatment.