<p>Calcium oxalate monohydrate (CaC₂O₄·H₂O) single crystals were successfully grown by the slow evaporation solution growth method under ambient conditions. The crystalline quality and phase purity were confirmed using Powder X-ray diffraction (PXRD), revealing a monoclinic crystal system with space group P2₁/c and preferential orientation. The sharp diffraction peaks and low microstrain values indicate good crystalline quality. Optical absorption analysis shows high transparency in the visible region with a wide optical band gap of 4.27&#xa0;eV, characteristic of an insulating material. The refractive index and birefringence analyses confirm optical anisotropy associated with the monoclinic structure and hydrogen bonding. The nonlinear optical properties were investigated using the <i>Z</i>-scan technique with a 532&#xa0;nm laser source. The open-aperture <i>Z</i>-scan results exhibit a symmetric valley profile, indicating third-order nonlinear absorption mechanisms such as two-photon absorption (TPA) or reverse saturable absorption (RSA), arising primarily from defect-assisted electronic transitions. Laser damage probability analysis based on Weibull statistics indicates moderate resistance to laser-induced damage with a defined threshold. The evaluated third-order susceptibility (<i>χ</i>³), nonlinear refractive index (<i>n</i>_<i>2</i>), and nonlinear absorption coefficient (<i>β</i>) confirm the presence of third-order nonlinear optical response in calcium oxalate monohydrate despite its centrosymmetric nature. These results indicate that the grown crystal may serve as a potential material for optical limiting and related third-order nonlinear optical applications, subject to further device-level investigation.</p>