Pre-stresses are frequently introduced into structures for a variety of reasons. Acoustoelastic techniques have been proposed to characterize the state of pre-stress in such structures. In plate-like structures the effect of stresses on the speed of propagation of guided waves can be exploited to characterize the state of pre-stress. In this study, the effect of pre-stresses with gradients on the propagation speed of guided waves is examined. In the context of acoustoelasticity, an isotropic plate with a pre-stress gradient behaves like a laminated anisotropic material. The acoustoelastic constants are a function of direction of wave propagation and are also dependent on the thickness coordinate. Acoustoelastic theory and laminated anisotropic plate theory are combined in this study. The inhomogeneity of constitutive behavior through the thickness of the plate is modeled suitably using a transfer matrix method. The effect of pre-stress gradient magnitudes on dispersion curves of symmetric and antisymmetric modes of guided wave propagation is demonstrated. Dispersion curves are presented for an aluminum plate as a function of magnitude and direction of applied pre-stress gradients.