Dissolved organic matter (DOM) scavenges sulfate radicals (SO 4 •- ), and SO 4 •- -induced DOM transformations influence disinfection byproduct (DBP) formation when chlorination follows advanced oxidation processes (AOPs) used for pollutant destruction during water and wastewater treatment. Competition kinetics experiments and transient kinetics experiments were conducted in the presence of 19 DOM fractions. Second-order reaction rate constants for DOM reactions with SO 4 •- ( k DOM,SO 4 •- ) ranged from (6.38 ± 0.53) × 10 6 M -1 s -1 to (3.68 ± 0.34) × 10 7 M C -1 s -1 . k DOM,SO 4 •- correlated with specific absorbance at 254 nm (SUVA 254 ) ( R 2 = 0.78) or total antioxidant capacity ( R 2 = 0.78), suggesting that DOM with more aromatics and antioxidative moieties reacted faster with SO 4 •- . SO 4 •- exposure activated DBP precursors and increased carbonaceous DBP (C-DBP) yields (e.g., trichloromethane, chloral hydrate, and 1,1,1-trichloropropanone) in humic acid and fulvic acid DOM fractions despite the great reduction in their organic carbon, chromophores, and fluorophores. Conversely, SO 4 •- -induced reactions reduced nitrogenous DBP yields (e.g., dichloroacetonitrile and trichloronitromethane) in wastewater effluent organic matter and algal organic matter without forming more C-DBP precursors. DBP formation as a function of SO 4 •- exposure (concentration × time) provides guidance on optimization strategies for SO 4 •- -based AOPs in realistic water matrices.