The constitutive modeling of shales is an important topic in the geomechanics community as it is often encountered in advanced applications such as nuclear waste storage, CO2 sequestration, and unconventional oil and gas exploitation. The goal of this work is to describe, within a unique plastic-damage framework, the full mechanical behavior of shales such as pre-peak hardening plasticity, non-linearity in the onset of inelastic strains, dilatancy, post-peak softening, and degradation of the elastic parameters. The model validation against three sets of triaxial experimental results on shale demonstrates its capability to reproduce the main mechanical characteristics.