Porous shape memory alloys are a new class of advanced materials with combined advantages of both shape memory alloys and porous materials. In order to manufacture a porous shape memory alloy with the desired mechanical properties, it is important to predict its mechanical properties before fabrication. In this paper, a new unit cell model is proposed to simulate the mechanical stress-strain response of porous shape memory alloys. Microplane theory is used to attribute mechanical constitutive relations of shape memory alloys to the bulk material, and the finite element method is employed for numerical simulations. The results show a good agreement with the experimental stress-strain behavior reported in the literature. The effect of pore volume fraction on the stress-strain response is also studied using the proposed approach. Random microstructures are generated in the FE model, and the effects of randomness on the mechanical behavior of porous shape memory alloys are also investigated for different values of pore volume fraction.