Lu(Nb,Ta)O4:Eu3+ powders are synthesized by a solid-state reaction process using LiCl and Li2SO4 fluxes. The photoluminescence (PL) excitation spectra of the synthesized powders consist of broad bands at approximately 270 nm and sharp peaks in the near ultraviolet region, which are assigned to the Nb5+-O2− charge transfer of [NbO4]3− niobates and the f-f transition of Eu3+, respectively. The PL emission spectra exhibit red peaks assigned to the 5D0 → 7FJ transitions of Eu3+. The strongest peak is obtained at 614 nm (5D0 → 7F2), indicating that the Eu3+ ions are incorporated into the Lu3+ asymmetric sites. The addition of fluxes causes the increase in emission intensity, and Li2SO4 flux is more effective for enhancement in emission intensity than is LiCl flux. The substitution of Ta5+ for Nb5+ results in an increase or decrease in the emission intensity of LuNb1-xTaxO4:Eu3+ powders, depending on amount and kind of flux. The findings are explained using particle morphology, modification of the [NbO4]3− structure, formation of substructure of LuTaO4, and change in the crystal field surrounding the Eu3+ ions.