Abstract <p>The paper examines phase transitions in the nickel-enriched Ni_57.2Mn_31.6In_11.2 Heusler alloy. This alloy exhibits a metamagnetostructural phase transition, with the Curie temperature of the ferromagnetic austenite phase close to the characteristic martensitic transition temperatures, which, in turn, affects the nature of the phase transformations. As the magnetic field increases from 0 to 1 T, vibration magnetometry data show a shift in the characteristic temperatures of the metamagnetostructural phase transition with a positive coefficient of sensitivity to magnetic field (<i>k</i>). In fields above 1 T, the sign of <i>k</i> reverses. The temperature for the onset of martensitic transformation upon application of a magnetic field increases at a rate <i>k</i>_Ms = 13&#xa0;K/T in magnetic fields from 0 to 1 T and decreases at a rate <i>k</i>_Ms = –0.8 K/T from 1 to 13 T.</p>