The negative-ion mass spectra of arylazo sulfides ArNNSR (1) show that their radical anions (1 •-), in competition with the fragmentation to aryl radicals, nitrogen, and thiolate anions, generate the radical anions of the corresponding sulfides (ArSR•-) and/or fragments therefrom. The competition between the two pathways above depends on the nature of the aryl moiety (possible presence and strength of electron-withdrawing substituents), on the nucleophilicity of the thiolate fragment, and on the stereochemistry [(E)- or (Z)-configuration] of the starting arylazo sulfide. The results are best interpreted through the possibility that 1 •- leads to ArSR•- through an electrostatically bonded thiolate ion−aryldiazenyl radical complex, in competition with dissociation of such a complex into separated species. A comparison with previous results on electrochemically induced reactions of 1 suggests that ion−radical pairs are key intermediates both in gas-phase and in solution.