The organic material, p-nitrophenol doped ammonium hydrogen oxalate hemihydrate was grown as single crystals at room temperature by slow evaporation solution growth technique in a constant temperature bath (± 0.01 °C). Doping by p-nitrophenol results in the partial substitution of an anion or a cation and causes changes in the physical properties of ammonium hydrogen oxalate hemihydrate. The grown crystals were characterized by XRD, FT-IR and FT-Raman spectral analyses. The UV–Vis–NIR spectrum was recorded to understand the range of optical transparency and the results showed its suitability for nonlinear optical applications. A shift in maximum absorption and a higher bandgap of 5.158 eV is observed. Dopant inclusion introduces nonlinearity in the sample. Z-scan studies show that the material exhibits saturable absorption rather than reverse saturable absorption as exhibited by its parent. Third order susceptibility and second order hyperpolarizability were calculated. Thermal properties of the crystals indicated that the material does not decompose before melting. The grown title compound shows normal dielectric behaviour when investigated at different frequencies and temperatures. The material is soft and produces etch pits when etched with acetone as etchant. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.