Tensile properties of intercritically annealed medium Mn steels containing 4.5 wt% manganese and two different carbon levels of 0.1 and 0.2 wt% are predicted using a composite iso‐strain model. In the predictions, the evolutions of phase fraction and retained austenite stability with annealing temperature are considered assuming ortho‐equilibrium phase fractions and full alloy partitioning during intercritical annealing. Predicted evolutions of ultimate tensile strength and uniform elongation values with variation in intercritical annealing temperature are compared to experimental results obtained following annealing for 1 h. The experimental results confirm the predicted dependence of the tensile properties on annealing temperature. While the product of ultimate tensile strength and uniform elongation has a linear relationship with the retained austenite fraction, experimental values exhibit a greater dependence on the retained austenite fraction than the predicted values.