The structural, elastic, and magnetic properties of NiR0.05Fe1.95O4 (R= Sm, and Gd) spinel ferrites were studied before, and after thermal neutron exposure. Polycrystalline NiFe1.95Gd0.05O4, and NiFe1.95Sm0.05O4 ferrites were synthesized using the standard ceramic method. The samples were irradiated by thermal neutrons using a rabbit system for 2 and 8 seconds with doses of 2.3 and 7.8 Gy, respectively. X-ray powder diffraction (XRD) revealed the formation of the cubic spinel phase with a secondary phase of RFeO3. XRD measurements indicated that by increasing the thermal neutron dose, the crystallinity of the prepared samples increases and the lattice parameter decreases. Fourier-transform infrared (FTIR) spectroscopy was utilized to examine the elastic properties, whereas, the elastic moduli and Debye temperature were obtained. Using a vibrating sample magnetometer (VSM), the effect of thermal neutron exposure on the magnetic properties was investigated. The saturation magnetization (Ms) increased by increasing the thermal neutron dose. The structure, elastic and magnetic parameters dependence on the thermal neutron dose may suggest that thermal neutron exposure can be used to fine-tuning these properties for particular applications.