Single crystals of bimetallic MnHg(SCN) 4 (abbreviated as MMTC) are grown by slow cooling method and the second and third order optical nonlinearities are investigated by Kurtz and Perry powder SHG test and single beam Z-scan technique respectively. The influences of SCN ligand in modifying the NLO properties are discussed and the results are compared with other organometallic crystals. The nonlinear refractive index, absorption coefficient and third order susceptibility are estimated to be −1.88×10 −11 cm 2 /W, 8.65×10 −6 cm/W and 6.58×10 −9 esu, respectively. The optical absorption of MMTC single crystal was recorded and the corresponding direct band gap is found to be 4.2eV. The phase matching and laser induced damage threshold studies are also carried out. The FT-IR and photoluminescence spectroscopic techniques were employed to identify the composition and luminescence nature of the crystal.