Reported here is a new protocol for the decarboxylative oxygenation of carboxylic acids using a non-heme manganese catalyst under blue light irradiation with O₂ as the sole oxidant. Featuring mild reaction conditions, the protocol allows readily available carboxylic acids to be converted into a wide variety of valuable aldehydes, ketones and amides. Mechanistic studies indicate that the decarboxylation and oxygenation involves the formation of active Mn-oxygen species.