Double annealing of low carbon medium Mn steel was studied. The second intercritical annealing was done at 650°C within a range of holding time: 3min to 30h. Tensile properties of the steel were measured as a function of holding time and the relation between microstructure and mechanical behavior was analyzed. Furthermore, a model, based on the mixture law combined with the considerations of equivalent increment of work in each microstructural constituent during mechanical loading, was proposed. The individual mechanical behavior of each considered microstructural constituent was described with the approaches existing in the literature. The complete model shows a very good agreement with the experimental stress-strain curves and predicts well the optimum strength-ductility balance after 2h holding.