A phenomenological hardening model based on the extended Voce law is proposed to capture the plastic flow of a third generation aluminium-lithium alloy. The model includes a simple precipitation law, which accounts for pre-ageing plastic deformation, and a hardening law that accounts for hardening of the matrix, and for the interaction of matrix glide dislocations with anisotropic and isotropic precipitates. Flow stress evolution in solution treated, underaged, and peak-aged samples is measured through uniaxial tensile tests on specimens cut at 0°, 45°, and 90° to the rolling direction. The measured flow stress evolution in all the tempers is captured well by the model. Model parameters offer insights into the sub-structural evolution that accompanies plastic deformation. © 2019 Elsevier Ltd.