This paper addresses an advanced and unified thermo-mechanical constitutive model for cohesive soils. Based on experimental evidence showing the non-linear and irreversible thermo-mechanical responses of saturated soils, the constitutive equations of the developed model, ACMEG-T, are presented. In the context of elasto-plasticity and critical state theory, the model uses the concepts of multi-mechanism and bounding surface theory. Non-linear thermo-elasticity is joined with two coupled thermo-plastic dissipative processes to reproduce all of the features of thermo-mechanical behaviour. The yield functions, the dissipative potentials and the plastic multipliers are introduced. Attention is particularly focused on the coupling between both plastic mechanisms, an isotropic and a deviatoric one, which are in agreement with the consistency condition for multiple dissipation. Finally, the efficiency of ACMEG-T is proven by validation tests on drained and undrained thermo-mechanical paths.