Crystalline nanoneedles of Eu³⁺-doped GdPO₄ and Eu³⁺-doped GdPO₄ covered with GdPO₄ shell (core shell) have been prepared at relatively low temperature of 150 °C in ethylene glycol medium. From luminescence study, asymmetric ratio of Eu³⁺ emission at 612 nm (electric dipole transition) to 592 nm (magnetic dipole transition) is found to be less than one. Maximum luminescence was observed from the nanoparticles with Eu³⁺ concentration of 5 at. %. For a fixed concentration of Eu³⁺ doping, there is an improvement in emission intensity for core-shell nanoparticles compared to that for core. This has been attributed to effective removal of surface inhomogeneities around Eu³⁺ ions present on the surface of core as well as the passivation of inevitable surface states, defects or capping ligand (ethylene glycol) of core nanoparticles by bonding to the shell. Lifetime for ⁵D₀ level of Eu³⁺ was found to increase three times for core-shell nanoparticles compared to that for core confirming the more Eu³⁺ ions with symmetry environment in core shell. For 5 at. % Eu³⁺-doped GdPO₄, quantum yield of 19% is obtained. These nanoparticles are redispersible in water, ethanol, or chloroform and thus will be useful in biological labeling. The dispersed particles are incorporated in polymer-based films that will be useful in display devices.