Single crystals of ammonium oxalate monohydrate (AO) were grown using the slow evaporation solution growth technique. The cell parameters obtained from the single crystal diffraction experiments matched with those known earlier showed that the grown crystals were composed of AO. The variation of dielectric constant as a function of frequency shows that the dielectric constant is relatively high in low frequency region and low in the high frequency region. Microhardness study indicates that the grown AO crystal is of a soft nature. The TG and DTA studies reveal that the grown crystal has good thermal stability and can be exploited in various applications up to 100 °C. There is a change in morphology of etch pits on prolonged etching. A very low value of dielectric constant supports that the material can be exploited in photonic and electro-optic devices. Thermal stability of the grown crystal is good.