Li2TiO3:Mn4+ has been previously identified as a potential candidate to replace commercial red-emitting Eu2+-activated phosphors. Its luminescent efficiency is limited by the presence of defects and the sensitivity of Mn4+ to redox processes. A series of co-doped Li2TiO3: x Mg2+, 0.01 Mn4+ samples were prepared to gain insight on the effect of electron doping on the structure and photoluminescent properties, through characterization by powder X-ray diffraction, elemental analysis, and optical spectroscopy. As Mg2+ substitutes for Li+, the ordered arrangement of cations within the honeycomb layers in the parent structure (Li2SnO3-type, an ordered derivative of rocksalt) gradually transforms to a more disordered arrangement. The increased cation site disorder leads to less intense and broader emission peaks as well as lower quantum yields.