A series of BaGdF₅:x% Tb³⁺,y% Sm³⁺ phosphors are synthesized by a hydrothermal method, taking the form of irregular nanospheres with average sizes of about 20 nm. An energy transfer from Tb³⁺ to Sm³⁺ is observed in the BaGdF₅:Tb³⁺,Sm³⁺ system, which is justified by the luminescence spectra. Simultaneously, a resonance-type energy transfer from Tb³⁺ to Sm³⁺ is demonstrated to occur via the dipole–dipole interaction, for which the critical distance (R_Tb–Sm) is calculated to be 13.49 Å. Furthermore, based on the rare earth concentrations and excitation wavelengths, multiple (white, orange red, green and green yellow) emissions are obtained by Sm³⁺ ion co-activated BaGdF₅:Tb³⁺ phosphors, which could make them good candidates to be used as full-color phosphors for nUV-LED. More importantly, the obtained samples also exhibit paramagnetic properties at room temperature and low temperature.