In this article, auto combustion prepared Ni1-xFexO (0≤x≤0.10) nanoparticles (NPs) have been investigated for their structural, morphological and optical properties. X-ray diffraction (XRD) studies reveal that all Fe doped NiO samples crystallize in single phase without any impurity. The crystallite size monotonically decreases from 20 nm to 10 nm with increasing Fe substitution. Transmission Electron Microscope images represent that the synthesized NiO NPs with size around 28 nm. A red shift in UV-Vis spectra indicates that band gap can be tuned by Fe doping from 3.76 eV to 2.51 eV because of the upward shifting of t2g level. The broad transmittance peak in Fourier transform infra-red spectra at 500 cm -1 is assigned to Ni–O stretching vibration mode. Differential scanning calorimetry curve revealed that the transition at 250 o C was exothermic because of structural relaxation. Copyright © VBRI Press.