We report that an electron beam focused for high-resolution imaging rapidly initiates observable crystallization of amorphous Me–Si–C films. For 200-keV electron irradiation of Nb–Si–C and Zr–Si–C films, crystallization is observed at doses of ~2.8 × 109 and ~4.7 × 109 e−/nm2, respectively. The crystallization process is driven by atomic displacement events, rather than heating from the electron beam as in situ annealing (400–600 °C) retains the amorphous state. Our findings demand a critical analysis of alleged amorphous and nanocrystalline ceramics including reassessing previous reports on nanocrystalline Me–Si–C films for possible electron-beam-induced crystallization effects.