An interesting nest-shaped heterobimetallic cluster [WOS3Cu3(4-pic)6]center dot ClO4 was synthesized and its structure determined by X-ray diffraction method. The nonlinear optical properties were investigated by Z-scan technique with 4 ns laser pulse at 532 nm wavelength. It reveals that the nonlinear absorption can be attributed to effective three-photon absorption and the nonlinear refraction is derived from the combination of the third-order and effective fifth-order nonlinearity. The sign and magnitude of third-and effective fifth-order nonlinearity were also evaluated. (C) 2009 Elsevier B.V. All rights reserved.