High-valent oxocobalt(IV) species have been invoked as key intermediates in oxidative catalysis, but investigations into the chemistry of proton-coupled redox reactions of such species have been limited. Herein, the reactivity of an established water oxidation catalyst, [Co4O4(OAc)(4)(py)(4)][PF6], toward H-atom abstraction reactions is described. Mechanistic analyses and density functional theory (DFT) calculations support a concerted proton-electron transfer (CPET) pathway in which the high energy intermediates formed in stepwise pathways are bypassed. Natural bond orbital (NBO) calculations point to cooperative donor-acceptor sigma interactions at the transition state, whereby the H-atom of the substrate is transferred to an orbital delocalized over a Co-3(mu(3)-O) fragment. The mechanistic insights provide design principles for the development of catalytic C-H activation processes mediated by a multimetallic oxo metal cluster.