A visible-light-driven Mn-catalyzed C(sp3)-H amidation of diphenylmethane derivatives with dioxazolones was described. These reactions occur with an external photosensitizer-free process and feature satisfactory to good yields (up to 81%) under mild conditions. Mechanistic investigations revealed that the reaction proceeded via a Mn-acyl nitrene intermediate and that H-atom abstraction was the rate-determining step. Computational studies showed that the decarboxylation of dioxazolone depends on the conversion of ground sextet state dioxazolone-bounding Mn species to quartet spin state via visible-light irradiation.