Non-rare earth Mn4+-doped oxide matrix phosphors are of increasing interest in the field of light-emitting diodes due to their good spectral properties. Herein, Mn4+-doped Mg2ScSbO6 phosphor was successfully synthesized via the conventional solid-state reaction method. The crystal structure of the sample was determined using a variety of characterization methods such as X-ray powder diffraction and Rietveld refinement analysis. The phosphor has a broadband absorption from near ultraviolet to blue light and emits deep red (similar to 682 nm) light of (2)Eg -> (4)A(2g) transition. The photoluminescence intensity and decay lifetime of the Mn4+-doped Mg2ScSbO6 are observed to be strongly dependent on temperature, and the results of quenching analysis were reported. The optimal Mg2ScSbO6:Mn4+ phosphor has a high color purity of 99.4% with an internal quantum efficiency value of 61.93% modulated by charge compensation of Li+ ions. The photoluminescence peak position of the phosphor can be well matched with the absorption peak of red and far-red phytochrome. Therefore, the deep-red-emitting phosphors have tremendous application merits and potential markets in plant growth.