In the present work, the role of Neodymium (III) nitrate hexahydrate [Nd (NO3)2] and lanthanum nitrate hexahydrate [La (NO3)3·6H2O] on the structural and radiation shielding properties of zircon mineral was examined. Therefore, a new La/Nb-doped ZrO2 nanocomposite was fabricated. Various experimental techniques such as energy-dispersive X-ray, scanning electron microscope, transmission electron microscopy, and X-ray diffraction pattern were utilized to discover the structure and chemical composition, as well as the morphology of the fabricated La/Nb-doped ZrO2 nanocomposites. Additionally, for the estimation of the fabricated composites' γ-ray shielding properties, Monte Carlo simulation was employed. Among low and intermediate γ-photon energy, the study affirmed a good shielding characteristic for the fabricated composites, where the linear attenuation coefficient reduced from 245.64 to 0.21 cm−1 when the γ-photon energy was raised respectively from 0.022 to 2.506 MeV. Compared to pure lead, the fabricated composites showed good shielding properties, where the shielding capacity reached 30–50% of the pure lead element in the 0.244–2.506 MeV intermediate energy interval.