Single-phase white light-emitting Ca BaLuSiO:Eu/Mn codoped phosphors were successfully synthesized, and their photoluminescence properties were experimentally determined. The analysis of the experimental results suggests that the partial substitution of Ba ions by smaller Ca ions alters the distribution of the Eu luminescence center among the three available Ba sites in the host lattice, which enables the emission to be efficiently tuned from blue to blue-green-yellow region. The incorporation of Mn ions resulted in a red light emission at around 618 nm, through energy transfer from Eu to Mn ions via dipole-dipole interactions. The incorporation of Ca and Mn ions also resulted in improved thermal stability. The results qualify the produced Ca BaLuSiO:Eu/Mn composition as a potential ultraviolet-convertible white light-emitting phosphor.