In the present work nanocrystalline NiFe2O4 samples were prepared by the sol-gel auto combustion technique. The synthesis was carried out by taking citric acid as fuel with metal nitrate to fuel ratio as 1:3. The obtained powder was annealed at 5500C for 4 h and then used for structural and magnetic investigations. Prepared nickel ferrite samples have been irradiated by gamma-ray (60Co) to examine the changes that occurred in structural properties. Structural properties of nickel ferrite nanoparticles before and after gamma irradiation were carried out by X-ray diffraction (XRD) technique. From the XRD pattern, it was observed that all the Braggs planes reveal cubic spinel structure before and after gamma irradiation. A close examination of the XRD pattern revealed the crystallite size of 21 nm and 19 nm for nickel ferrite samples before and after gamma irradiation respectively. The obtained results help in providing interesting and useful study for various applications of nickel ferrites.