The third‐order optical nonlinearity &khgr;(3), linear absorption coefficient &agr;, and the two‐photon absorption coefficient &bgr; of two nickel dithiolene complexes are reported. The nonlinearities were measured at 1064 nm using 100 ps pulses. Molecular nonlinearities 103times those of carbon disulphide were observed. Two figures of merit were calculated from the data &Dgr;nsat/&agr;&lgr;=5 andn2/2&bgr;&lgr;≳2, where &agr; and &bgr; are the linear and two‐photon absorption coefficients andn2the nonlinear refractive index. These figures are compatible with those required for simple all‐optical switching devices.