This paper is focused on the characterization and modeling of a commercial Ni–Mn–Ga alloy for use as a dynamic deformation sensor. The flux density is experimentally determined as a function of cyclic strain loading at frequencies from 0.2 to 160 Hz. With increasing frequency, the stress versus strain response remains almost unchanged whereas the flux density versus strain response shows increasing hysteresis. This behavior indicates that twin-variant reorientation occurs in concert with the mechanical loading, whereas the rotation of magnetization vectors occurs with a delay as the loading frequency increases. The increasing hysteresis in magnetization must be considered when utilizing the material in dynamic sensing applications. A modeling strategy is developed which incorporates magnetic diffusion and a linear constitutive equation. The model is used to describe the hysteretic dependence of magnetic flux density on strain at dynamic frequencies.