Abstract Allylthiourea cadmium chloride, a promising non-linear optical material was grown from aqueous solution by slow evaporation technique. Single crystal X-ray diffraction studies reveal that the crystal is trigonal structure with R3 C space group. The spectroscopic properties were investigated by recording the Fourier transform infrared and optical absorption spectra. The dielectric studies of the sample were carried out at varying temperatures in the frequency range from 50 Hz to 5 MHz. The thermal properties were studied using thermogravimetric analyses and photopyroelectric technique. It is evident from the thermal studies that the decomposition of the crystal begins around 200 °C. The microhardness test conducted on the grown crystal suggests that the crystal has a relatively high mechanical strength. The second harmonic generation efficiency of the crystal was studied and found to be nearly 1.5 times that of urea.