Abstract <p>CeO₂/PAA and Cd²⁺ substituted CeO₂/PAA nanocomposites (NCs) have been synthesized by in-situ chemical method. For all of the nanocomposites, X-ray diffraction (XRD) studies confirm the cubic structure of CeO₂. The scanning electron microscopy (SEM) shows that the CeO₂ nanoparticles (NPs) are spherical in shape and aggregate less with increasing Cd²⁺ ion concentration. The construction of nanocomposites containing Cd²⁺ substituted CeO₂ and poly acrylic acid (PAA) is confirmed by Fourier transform infra-red (FTIR) spectra. The absorption spectra show the blue shifted phenomenon. The two emission bands ascribed to near band edge emission and blue emission are visible in photoluminescence spectra. The Z-scan technique was used to conduct nonlinear optical studies on CeO₂/PAA and Cd²⁺ substituted CeO₂/PAA NCs. The third order nonlinear optical susceptibility and figure of merit of CeO₂/PAA NCs increase with increasing Cd²⁺ substitution concentration and are found to be 3.486 × 10^–5 and 1.660 × 10^–8 esu m for Ce_0.09Cd_0.01O₂/PAA NCs. The nonlinear optical coefficients are higher than previously reported values for other nanocomposite materials. The current findings suggest that Cd²⁺ substituted CeO₂/PAA NCs is a feasible material for the fabrication of nonlinear optical devices.</p>