A copper complex constructed by the ligand: 1,3-dithiole-2-thione-4,5-dithiolato (DMIT) has been synthesized and its crystal structure has been determined by means of X-ray single crystal diffraction. The central copper(11) ion coordinates with two OMIT which constructed a square environment. Intermolecular C-H center dot center dot center dot S hydrogen bonds between cation groups and ligands lead to the formation of a two-dimensional supramolecular network. Its third-order nonlinear optical property has been studied using Z-scan technique at different peak laser irradiance with 20 picosecond (ps) pulses at wavelength 1064 nm. Its molecular second hyperpolarizability gamma was determined to be 4.03 x 10(-57) m(4) CV(-3). (C) 2011 Elsevier B.V. All rights reserved.