A phenomenological model to simulate the two-way shape memory effect (TWSME) in nickel-titanium alloys (NiTi) is proposed. The model is based on the Prandtl–Ishlinksii operator and it is able to simulate the hysteretic behavior of the material in the strain-temperature response. Starting from some experimental measurements of well known thermomechanical characteristics of NiTi alloys, the parameters of the phenomenological model are identified by simple and efficient numerical procedures. The model was developed in the commercial software package SIMULINK ® and it is able to simulate the effects of applied stresses on the TWSME as well as partial thermal cycles, which generate incomplete martensitic transformations. A systematic comparison between experimental measurements, carried out under different values of applied stress, and numerical predictions are illustrated for both complete and incomplete phase transformations. The results are considered satisfactory both in accuracy and in computational time; therefore, the method is robust and suitable for use in real-time applications.