Rare earth ion (Tb3+)-doped zinc ferrite (ZnFe2O4) nanoparticles grown on reduced graphene oxide (RGO) prepared through sol-gel method have been reported. During the sol-gel process, graphene oxide was reduced to RGO, and, subsequently, anatase TiO2 and cubic spinel ZnFe2-x Tb (x) O-4 were grown in situ on the surfaces of the RGO nano-sheets. The structure, surface morphology and chemical composition of ternary nano-composites were studied using scanning electron microscopy, energy-dispersive X-ray, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, photoluminescence spectra and vibrating sample magnetometer (VSM). XRD results showed that the produced TiO2 was composed of anatase and some rutile phases and ZnFe2O4 with a cubic spinel structure. The particle sizes of ZnFe2O4 and TiO2 nanoparticles were in the ranges of similar to 65-80 and similar to 17-20 nm, respectively. The saturation magnetization (M (S)) determined from VSM was found to linearly increase with Tb3+ concentration.