We have systematically studied the mechanical stability of group V transition metal carbides TMC 2 (TM = Hf, Ta, W, Re, Os, Ir, Pt, and Au) in the pyrite and fluorite phase, by calculating their elastic constants within the density functional theory scheme. It was found that all but ReC 2 and OsC 2 are stable in pyrite phase. On the other hand, all metal carbides studied were unstable in the fluorite phase.