The controllable divergent reactivity of 1,3-dicarbonyls is described, which enables the efficient hydro- and oxo-alkylation of vinyl arenes. Both reaction pathways are initiated through the formation of polarity reversed C-centered-radical intermediates at the active methylene center of 1,3-dicarbonyls via direct photocatalytic C-H bond transformations. The oxoalkylation of alkenes is achieved under aerobic conditions via a Cu(II)-photo-mediated rebound mechanism while the corresponding hydroalkylation becomes possible under nitrogen atmosphere by the combination of 4CzIPN and a Brønsted base. The breadth of these divergent protocols is demonstrated in the late-stage modification of drugs and natural products, and by the transformation of the products to a variety of heterocycles such as pyridines, pyrroles, or furans. Moreover, the two catalytic modes can be combined synergistically for the stereoselective construction of cyclopenta-nol derivatives in a formal [4+1]-annulation process.