Thin films of Ni-Mn-Sn ferromagnetic shape memory alloy, grown on Si substrate by DC magnetron sputtering were bombarded by 450 keV Ar(+4) ions at different fluences ranging from 1x10(14) to 3x10(16) ions/cm(2) in order to investigate the effect of ion irradiation on characteristic transformation temperatures and thus on shape memory behavior. Temperature dependent resistivity measurements reveal the increase in martensitic transformation temperature (similar to 100 K) upto a fluence of 1x10(15) ions/cm(2), above which shape memory behavior degrades and completely loses its behavior at 3x10(16) ions/cm(2), which is ascribed to the amorphization of Ni-Mn-Sn structure at a fluence of 3x10(16) ions/cm(2) as evidenced from X-ray diffraction pattern. The diffuse rings in the electron diffraction pattern also confirmed the amorphization of the film at highest fluence. The temperature dependent magnetization measurements also show the increase in martensitic transformation temperature upto a fluence of 1x10(15) ions/cm(2) in support of resistivity data. This work gives a possibility to acquire a better control on the properties of FSMA thin films using ion irradiation. (C) 2011 Elsevier B.V. All rights reserved.