Light-beam profile deformation during scattering with the photorefractive grating formed by the diffusive, photovoltaic, and drift mechanisms is investigated in the case of anisotropic Bragg diffraction for the incident light with arbitrary spatial beam profile under the framework of a three-dimensional configuration. A set of three-dimensional coupled-wave equations that can properly describe the interaction is derived from Maxwell’s equations. In the wave equations, the permittivity profile, which is perturbed by the diffusive, photovoltaic, and drift mechanisms, can be correctly plotted by employing Kukhtarev’s material model. Using a spatial Fourier transform technique identical to the one used in deriving the spatial transfer function from the paraxial wave equation for free-space propagation, a steady-state solution for the output light beams diffracted by this initially stored grating can be calculated in the spatial frequency domain. The nature of the dependence of beam profiles on the material properties, sample thickness, and incident angle, under the combined effects of propagational diffraction, diffusion, photovoltaicity, and drifting, is presented.