A highly efficient nonlinear optical single crystals of tetrathiourea mercury (II) tetrathiocyanato zinc(II), Hg(N2H4CS)(4)Zn(SCN)(4), (TMTZ) were conveniently grown from mixture solvent of ethanol-water by slow evaporation technique. The grown crystals exhibited needle-shaped morphology. The cell parameters of TMTZ single crystals were determined by single-crystal X-ray diffraction. The grown crystals were subjected to optical characterization by FT-IR, FT-Raman and UV-Vis-NIR techniques. The dielectric study of TMTZ showed low dielectric loss in the high-frequency region. The photoconductivity studies confirm that the TMTZ crystal has negative photoconducting nature. (c) 2005 Elsevier B.V. All rights reserved.