The preparation and crystal structure of a novel nonlinear optical organometallic crystal, benzyltriethylamine bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickel(III) (BTEANDT), are described. The crystal was characterized by elemental analyses, infrared and X-ray powder diffraction spectroscopy, thermal analysis and optical absorption. The third order nonlinear optical properties of crystal were investigated by using the Z-scan technique at 1064 nm with 20 ps. A self-focusing effect and a saturable absorption were observed. The nonlinear refraction coefficient (n(2)) and the nonlinear absorption coefficient (beta) have been found to be 7.311 x 10(-18) m(2)/W and -6.064 x 10(-11) m/W when the on-axis irradiance at focus (I-0) is 3.025 GW/cm(2). The relationship between beta and I-0 was studied, which has revealed that the former is proportional to the latter. The result has been explained with the theory of absorption cross-section. (C) 2010 Elsevier B.V. All rights reserved.