<p>Sodium-doped potassium zinc sulfate hexahydrate (Na-doped KZSH) single crystals, belonging to the family of inorganic Tutton’s salts, were successfully grown by the slow evaporation solution growth technique at room temperature for potential nonlinear optical (NLO) applications. The crystalline perfection and unit cell parameters of the as-grown crystals were determined using single crystal X-ray diffraction analysis. The vibrational modes and functional groups were identified through Fourier Transform Infrared (FTIR) spectroscopy. The surface morphology and compositional analysis, including confirmation of sodium incorporation, were carried out using Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Analysis (SEM–EDAX). Furthermore, the chemical states and electronic environment of the constituent elements were investigated using X-ray Photoelectron Spectroscopy (XPS). Absorbance and the bandgap energy value at 5.83 eV were evaluated using UV–Visible spectroscopy, which confirmed the optical quality of the crystal. Photoluminescence studies revealed a broad emission peak at 340 nm, with corresponding chromaticity coordinates (CIE-1931), and the calculated Correlated Color Temperature CCT (K) value was 1792.04 K, indicating blue–violet emission. The thermal stability of the crystal was assessed through Thermogravimetric–Differential Thermal (TG–DTG) and Differential Scanning Calorimetry (DSC) analysis, confirming stability up to 90 °C. The Laser-Induced Damage Threshold (LDT) measurements yielded a high power density of 12.023 GW/cm², highlighting the mechanical robustness of the crystal. Nonlinear optical properties were further examined using the Z-scan technique, which confirmed significant third-harmonic generation (THG) efficiency. Notably, the obtained NLO response was found to be superior to that of the widely studied potassium dihydrogen phosphate (KDP) crystal, establishing Na-doped KZSH as a promising material for advanced photonic and optoelectronic applications.</p>