A new metal-organic nonlinear optical dibromo bis(triphenylphosphine oxide) mercury(II) (HgBr(2)(TPPO)(2), TPPO=triphenylphosphine oxide) crystal has been synthesized. Single-crystal X-ray diffraction reveals that HgBr(2)(TPPO)(2) crystallizes in the orthorhombic system, space group Pna2(1), a=21.174A, b=9.1979A, c=17.468A, and Z=4. The crystal was also characterized by FTIR spectroscopy, differential scanning calorimetry (DSC), thermal gravity analysis (TGA), and UV-vis-IR spectroscopy. Thermal analyses confirmed that the crystal is stable up to 151 degrees C. The transmission spectrum of the crystal shows that the lower cut off wavelength lies at 340nm. The nonlinear optical (NLO) property of HgBr(2)(TPPO)(2) has been estimated by Kurtz-powder second harmonic generation (SHG) test.