An N-heterocyclic carbene (NHC)-catalyzed facile assembly of α-sulfonyl ketones has been successfully developed through a radical-mediated sulfonyl methylation of readily available aldehydes. This protocol involves the effective single-electron transfer reduction of α-iodosulfones by NHC-bound Breslow intermediates, thus allowing a subsequent radical-radical coupling to afford the target compounds. Moreover, the catalytic system was found to be equally effective for difunctionalization of styrenes and 1,3-enynes via a three-component radical relay process.