A physical based model is developed to describe the plastic deformation of Ti5553 from 800 °C to 920 °C and strain rates from 0.001 s-1 up to 10 s-1. The model describes both, the microstructure evolution and the flow stress. The microstructural model is based on a coupled set of rate equations for dislocation densities, misorientation distributions and fractions of high and low angles grain boundaries. The total dislocation density is considered to be the sum of different types of dislocations, namely immobile, mobile and wall dislocations. Their evolution rates are based on the effects of production of dislocations during deformation, dynamic recovery, continuous dynamic recrystallisation as well as static recovery phenomena. The model describes the flow stress evolution using constitutive equations that calculated the thermal and athermal stresses of the α- and the β-phases. The overall flow stress is calculated as a sum of the contributions of the equivalent flow stress of the α-phase and the β-phase. Dynamic phase transformation and continuous dynamic recrystallisisation are responsible for the flow softening and implemented in the model. The model is validated with hot compression and hot torsion tests, as well as with microstructural characterization of deformed and non-deformed samples.