Slow evaporation solution growth technique was used to grow cadmium mercury thiocyanate (CMTC), an organometallic thiocyanate crystal. Single crystal XRD and FTIR spectroscopic analyses confirmed the CMTC compound formation. The grown crystal was characterised for linear optical properties, photoluminescence, thermal stability, dielectric properties, mechanical stability and surface quality. The single-beam Z-scan technique, employing a 532 nm diode-pumped Nd:YAG laser of 50 mW, was used to study the third-order nonlinear optical properties and the optical limiting behaviour of the novel semi-organic CMTC crystal. The nonlinear refractive index (n2), the nonlinear absorption coefficient (β), and third-order nonlinear susceptibility (χ(3)) were calculated to be 8.89×10-8(cm2W-1),0.021×10-4(cmW-1) and 14.27 × 10 - 6 (esu) respectively. Studies on the optical limiting behaviour of the title compound show the linear variation of output power with respect to input power at low intensities and start saturating at higher intensities. The optical limiting threshold value of the title crystal was found to be 31.3 mW. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.