Organic single crystals, with their exceptional nonlinear optical properties and highly tuneable characteristics, are increasingly recognized as promising materials for photonic and optoelectronic applications.In this study, p-nitro phenol p-amino benzoic acid monohydrate (PNPAB) single crystals were successfully grown using the slow evaporation solution technique.Methanol was utilized as the solvent, and the crystal growth process was carefully controlled at a constant temperature to promote uniformity and defect free formation.Crystal's lattice structure was unveiled through single crystal X-ray diffraction, and crystalline integrity meticulously examined with high-resolution X-ray diffraction.Spectral anal. using Fourier transform IR techniques was conducted to determine presence of functional groups.UV-Vis anal. of PNPAB crystal showed an absorption edge at 406 nm with a band gap of 3.05 eV, while photoluminescence displayed emission at 435 nm upon 378 nm excitation, indicating potential for optoelectronic applications.Third-order nonlinear optical (TONLO) properties were explored using an ultrafast (40-fs) laser at 800 nm, employing both open and closed aperture Z-scan techniques.PNPAB is identified as a highly promising material for optical limiting applications due to its unique properties and effectiveness in managing excessive light levels.