Herein we report a photo‐mediated formal addition of carboxylic acids to activated alkenes catalyzed by a pyrimidopteridine photoredox catalyst. The decarboxylation of aliphatic carboxylic acids upon single‐electron oxidation is countered in the presence of electron‐rich alkenes and a hydroacetoxylation is observed. Mechanistic proposals have been made based on CV measurements, competitive Stern‐Volmer quenching and EPR experiments. Evidence that tetra‐N‐substituted pyrimidopteridines function as dual photoredox and hydrogen atom transfer catalyst was supported by spectroscopic means.