Research interest in the thermo-mechanical behaviour of soils is growing as a result of an increasing number of geomechanical problems involving thermal effects. This paper concerns the constitutive modelling of non- isothermal mechanical behaviour of clayey soils. An elastoplastic model is extended to non-isothermal conditions to account for non-linearities and hardening that occurs as a result of heating of soils. This constitutive model includes evolution of the yield limit with temperature through a dependency law for preconsolidation pressure, with respect to heating. Numerical simulations support the theoretical aspects of the paper by demonstrating the ability of this non- isothermal constitutive law to represent the complete behaviour of clayey soils at different temperatures and stress states. Therefore, the model can be used for quantitative predictions of thermo-mechanical behaviour of clayey soils.