This paper presents a method allowing the simultaneous identification of parameters governing an orthotropic law with a nonlinear shear response. Such laws appear for instance through the thickness of thick laminated composites. The tested specimen is subjected to boundary conditions similar to those of a Iosipescu setup. The strain field in the central area is processed with the so-called virtual fields method, which is an application of the principle of virtual work with particular virtual fields. The method is simulated with data obtained from finite element calculations.