The magnetostriction measurements of almost stoichiometric single crystalline Ni
_2
MnGa compound with
T_m<T_C
(
T_m
and
T_C
are the martensitic and ferromagnetic transformation temperatures respectively) at constant temperatures have been performed in a temperature range of 100--400 K. The measurements resulted in a temperature evolution of magnetostrain,
\varepsilon
, with two extremums caused by soft mode condensation and martensitic transformation. Magnetic field induced strain of 0.4% In turn, the dilatometric mode of measurements along [100] under magnetic field (either constant or cyclic) led to 1.5% strain in martensite. Using a phenomenological approach both the anisotropic and volume magnetoelastic constants have been evaluated in cubic phase to be equal to
-
1.2 MPa and
-
0.4 GPa respectively. The experimentally observed smearing of Curie temperature in single crystalline Ni
_{51.2}
Mn
_{31.1}
Ga
_{17.7}
alloy with
T_m>T_C
is quantitatively explained by the spatially inhomogeneous mass density of martensitic phase and volume magnetostriction.
