An organic nonlinear optical (NLO) crystal of ammonium p-toluenesulfonate (AMPTS) was grown by a slow evaporation solution growth technique. A single crystal X-ray diffraction study revealed that the AMPTS crystal belongs to orthorhombic system with the space group of Pna21. From the UV–Vis–NIR spectral study, refractive index and extinction coefficient were determined. The nonlinear refractive index, nonlinear absorption coefficient and third-order NLO susceptibility were calculated to be −5.2872 × 10−8 cm2/W, 7.035 × 10−3 cm/W and 3.44 × 10−6 esu, respectively, by Z-scan studies. The laser damage threshold of AMPTS crystal was found to be 4.08, 4.0 and 3.95 GW/cm2 for (10−1), (−110) and (001) planes, respectively, using a Nd:YAG laser source. Etching study revealed the surface quality of AMPTS crystal.