The stability of carbon nanotubes (CNTs) under ion irradiation is an important parameter for the performance of CNT devices under extreme conditions of heat, radiation, etc. In order to investigate the stability and the evolution of nature of bonding, multiwalled carbon nanotubes were irradiated using 21keV Ag − ions with fluences of 1×10 13 , 5×10 13 , 7×10 13 and 1×10 14 ions/cm 2 . The samples were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The graphene wall structure of the nanotube is found to sustain up to a fluence of 7×10 13 ions/cm 2 . Further increase of ion fluence leads to the destruction of the graphene wall structure. Increasing ion fluence in irradiation is found to lead to an increased number of sp 3 hybridized carbon atoms compared with the pristine sample.