Abstract Herein, we present a (NH 4 ) 2 S 2 O 8 mediated difunctionalization reaction of aryl alkenes with quinoxalinones and P(O)SH compounds. This method enables the synthesis of various phosphorothioate‐containing quinoxalin‐2(1 H )‐one derivatives (46 examples) in 37–79% yields. The reaction is compatible with a range of functional groups and is easily adaptable to large‐scale synthesis. Preliminary studies suggest the involvement of phosphorothioate radicals in these transformations.