Nanoparticles of Tb³⁺-doped GdPO₄ (Tb³⁺ = 0, 2, 5, 7, 10, and 20 atom-%) have been prepared at a relatively low temperature of 160 °C in ethylene glycol, medium. The particles crystallize in a monoclinic structure with an average crystallite size of 30-50 nm. From the luminescence study of Tb³⁺doped GdPO₄, the magnetic dipole transition (⁵D₄®⁷F₅) at 545 nm (green) was found to be more prominent: than the electric dipole transition (⁵D₄®⁷F₆) at 484 nm (blue). Maximum luminescence intensity and lifetime was observed for 7 atom-% Tb³⁺. Above 7 atom-% Tb³⁺, a decrease in luminescence was observed. This has been attributed to a con-centration-quenching effect due to the cross-relaxation among Tb³⁺ ions. The highest luminescence intensity of Tb³⁺ was observed after excitation at: 274 nm ( ⁸S_7/2® ⁶I_11/2 of Gd³⁺) among various excitation wavelengths (including f-f absorptions of Tb³⁺). This is due to an efficient transfer of energy from. Gd³⁺ to Tb³⁺ that: shows GdPO₄ to be a potential host for Tb³⁺. These nanoparticles are found to be redispersible in water and ethanol and are incorporated into polyvinyl alcohol film homogeneously. This film showed bright green emission.