Multimetallic complex phosphate K2Gd1−xZr(PO4)3:Tbx3+ (0 ≤ x ≤ 50) synthesized by solid state diffusion exhibit intense green fluorescence and paramagnetic behaviour. Monophasic particles of dimensions ranging from few hundred nanometers to few micrometers could be obtained. Photo excitation at 274 nm corresponding to Gd3+ transition8S7/2–6IJ and Gd3+–Tb3+ charge transfer followed by emission from 5DJ(J = 3,4) to 7FJ(J = 3,4,5,6) levels of Tb3+ ions is observed to be the most effective photoluminescence mechanism. Paramagnetic nature was proved by VSM study. Variation of paramagnetism in undoped K2GdZr(PO4)3 and K2Gd1−xZr(PO4)3:Tbx3+ particles and quantitative analysis by EPR indicate the role of unpaired 4f electron spin of trivalent rare earth ions in the lattice for making the particles paramagnetic.