The cubic phase of Magnesium oxide (MgO) nanoparticles is synthesized by the sol-gel method. The nanoparticles were subjected to annealing at 500 degrees C to enable stress and strain analysis. Characterization of the annealed nanoparticles was performed using powder X-ray diffraction (XRD). Through analysis of the XRD peak profile, key properties, such as crystallite size, lattice strain, deformation stress, and deformation energy density, were determined. These parameters were estimated using three models such as the Williamson-Hall-Isotropic Strain Model (W-H-ISM), the Williamson-Hall-Anisotropic Strain Model (W-H-ASM), and the Williamson-Hall-Energy Density Model (W-H-EDM). The estimations were based on the W-H plot derived from the powder XRD data. The findings of this study contribute to a better understanding of the structural and mechanical characteristics of annealed MgO nanoparticles, thus informing their potential applications. C1 [Srinivasan, R.; Karthikeyan, N.; Thiruramanathan, P.] Ramco Inst Technol, Dept Phys, Rajapalayam 626117, India. [Arun, T.] Univ Atacama, Sede Vallenar, Costanera 105, Vallenar 1612178, Chile. [Bose, A. Chandra] Natl Inst Technol, Dept Phys, Tiruchirappalli 620015, India. C3 Universidad de Atacama; National Institute of Technology (NIT System); National Institute of Technology Tiruchirappalli