This work reports the sol–gel synthesis of zirconia (ZrO 2 ) nanoparticles (NPs) in which the effect of varying molarities of zirconium oxychloride salt (such as 0.025 M, 0.050 M, 0.075 M, 0.100 M, and 0.125 M) has been investigated on the structural, mechanical, and optical characteristics by maintaining a basic pH at 9. All experimental conditions were conducted using basic media, with XRD, SEM, hardness, and optical analysis performed. Structural analysis, which was performed by using an X-ray diffractometer, reveals the formation of mixed phase zirconia (tetragonal and monoclinic) under as-synthesized conditions. Optical analysis shows that transmission increases as the molarity grows. The refractive index and extinction coefficient conform to the normal dispersion behavior, while the refractive index is observed to increase as the molarity becomes large. A high value of the refractive index of about 1.65 and lowest value of band gap 3.96 eV have been observed at a molarity of 0.075 M in the UV region. The hardness is observed to be continuously increased as the molarity grows, wherein the maximum hardness of 1167 HV is observed at a molarity of 0.075 M within the considered molarities (0.025 M, 0.050 M, 0.075 M, 0.100 M, and 0.125 M).