Herein, we have developed visible-light photoredox-catalyzed decarboxylating carboxylic acids for alkylation of heteroarenes under mild conditions. The transformation occurred smoothly without the requirement of stoichiometric oxidants in the presence of 0.3 equiv of base, which benefited from the release of hydrogen (H) and carbon dioxide (CO). Various substrates and functional groups were tolerated. Primary mechanistic studies suggest that an oxidative quenching pathway and a reductive quenching pathway are both possible in the catalytic cycle.