Results of the study of the effect of various types of plastic deformation on microstructural features and change in physical and mechanical properties of the nonstoichiometric Heusler alloy Ni_47Mn_42In_11 are shown. It was demonstrated that the deformation by rolling and upsetting leads to an increase in the microhardness and to an embrittlement of the investigated alloy. Severe plastic deformation by torsion under high pressure of 8 GPa at room temperature was found to strongly refine initially coarse grain and to contribute to the formation of a nanocrystalline structure with grain fragments up to 10 nm. In this case, the fraction of viscous constituent on the fracture and the microhardness increased, while the magnetic susceptibility decreased.