<p>In the presence of water, geomaterials, such as rocks and soils, may undergo a process of mineral dissolution, depending on the composition of solid minerals. Mineral dissolution increases the porosity, decreases the stiffness, and alters the hydraulic permeability of the material. In the present research, we develop a model for the study of mechanical behavior of fluid-saturated geomaterials undergoing mineral dissolution. An internal variable is introduced in the constitutive equations to account for the effects of mineral dissolution on the mechanical response of the material. The internal variable evolves with time, and its evolution equation is derived from the rate equation for dissolution. The mechanical properties of the material are dependent on this internal variable, and the Mori–Tanaka scheme is used to estimate the bulk and shear moduli of the material subject to mineral dissolution. Further, we present a mixed finite element formulation for solving a set of coupled governing equations. Finally, as an illustrative example, we examine a benchmark problem in soil mechanics to show the interactions between mineral dissolution, pore pressure diffusion, and solid deformation.</p>