Abstract FexZn0.95-xCr0.05O nanoparticles have been obtained for the different concentrations of Fe ions by using the sol-gel method. The hexagonal wurtzite structure of all the samples was confirmed by Rietveld refined X-ray diffraction patterns. The addition of Fe ions decreased lattice constants a and c from 3.2487 to 3.2474 Å and 5.2043 to 5.2029 Å, respectively. Uniform deformation, uniform stress deformation, and uniform deformation energy density models were assumed to obtain the crystallite size and strain values from Williamson-Hall analysis. The average crystallite size obtained from all four methods showed increasing variation with the addition of Fe ions in Zn-Cr-O, which was found in good agreement with the Scherrer equation, scanning electron microscopy, and high-resolution transmission electron microscopy results. Energy-dispersive X-ray spectra of typical samples confirmed the stoichiometric proportion of constituent elements. Room temperature ferromagnetism was observed in all the Fe-free and Fe-doped samples. Optical studies were carried out by UV-visible spectrophotometry. The band gap values lay in the range of 3.275 to 3.215 eV.