The heterometallic cluster [WM 2 S 4 (Pph 3 ) 3 ]·DMF (M 2 =1.25Ag+0.75Cu) 1 has been synthesized by low-temperature solid-state reaction. Single crystal X-ray analyses reveal that compound 1 possesses a linear skeleton with a W center slightly distorted from the tetrahedron. The compound was characterized by elemental analyses, IR spectra and UV–visible spectra. The third-order nonlinear optical (NLO) properties were also investigated and they exhibit nice nonlinear absorption and self-defocusing performance with modulus of the hyperpolarizability 9.8×10 −30 esu for 1.