Shape memory alloys (SMAs) are a well-known type of smart material that recovers its original shapes upon activation. This unique property makes SMAs attractive for pre-stressing applications in civil engineering. Iron-based SMAs (Fe-SMAs) are particularly promising for civil engineering applications because of their low cost, high stiffness, and large recovery force generation. The activation of Fe-SMAs embedded in concrete involves four main physical processes: electrical current flow, heat generation and transfer, stress generation, and phase transformation. A multiphysical simulation of the Fe-SMA activation is performed in the present study, considering the interaction of the involved physical models. The verification of the model is done in multiple steps, by comparing the simulation results with the available experimental results on Fe-SMA activation. Following the model verification, a parametric study is done to investigate the effective activation, and geometrical parameters on the heat, and stress distributions. The model provides a reliable tool for understanding the behavior of the embedded Fe-SMA reinforcement and surrounding concrete during activation. It also aids in designing the appropriate activation and geometrical parameters for SMA-reinforced concrete structures, based on the required mechanical properties of the structure.