We have successfully developed a general protocol for the photoredox-catalyzed radical group transfer of vinyl and alkynyl silanes. Our method enables the incorporation of alkenes and alkynes on sp 3 positions, using either activated or unactivated alkyl iodides as radical precursors. The protocol exhibits high diastereoselectivity and broad functional group tolerance, and does not require the use of a fluoride source to drive the ring-opening of the cyclic siloxane intermediate. Having investigated the mechanism for the formation of silicontethered radical cyclization intermediates, we have identified the multiple roles played by silicon in diverting the reaction pathway towards an overall redoxneutral radical group transfer reaction. We expect that this divergent reactivity of silicon-based radical acceptor groups can be exploited in the synthesis of complex molecular scaffolds through radical cyclization/fragmentation strategies.