The present work developed a radical relay model for cross-coupling reactions involving multi-radical systems. The photosensitized difunctionalization of styrene with oxime carbonate was used as a model reaction to examine the regio- and chemoselectivity of radical addition processes. In this model mechanism, a photosensitizer molecule absorbs a photon to generate an excited state, following which a triplet–triplet energy transfer process results in an excited oxime carbonate intermediate. The subsequent cleavage of an N–O bond generates alkoxycarbonyloxyl and iminyl radicals whereupon the former, which is a stronger electrophile, preferentially adds to styrene. Variations in the relative concentrations of the two radical species determine the chemoselectivity of the cross-coupling reaction.