Cerium oxide is widely used in chemical mechanisms, fuel cells, etc. on the other hand yttrium oxide nanoparticle is acquainted with practical applications because others have higher dielectric constant and thermal stability, both are rare and noble earth metals. In this study, YCeO nanocomposites were efficaciously synthesized by the hydrothermal method in the company of sodium hydroxide as a reducing agent as well as cerium nitrate and yttrium nitrate as a precursor. Synthesis temperature and pressure, during hydrothermal reactions, show a critical role in governing the shape, size, oxygen vacancy attentiveness, and low-temperature reducibility in CeO2-based nanocomposites. The lattice constants of the ceria nanocomposite also are contingent upon the attentiveness of hydroxide ions which primes to better morphology at low temperatures and pressure. XRD pattern of YCeO shows the Cubic structure of space group Fm3m having density 6.74gmcm^-3, volume 157.81*10⁶pm³, crystallite size 18.66nm and lattice strain is 0.0041 and many more structural parameters were calculated. FE-SEM and AFM studies show the granular structure and surface roughness. Surface porosity and specific surface area were observed by BET, average nanoparticle size was analyzed by the analyzer, and optical properties were observed by FTIR and showing various chemical groups and UV-Visible with band gap 3.27eV and absorbance at 256.58nm lastly thermal stability of this nanoparticle was analyzed by TGA.