Major weakness of all carbon-based materials originates from their poor oxidative stability. The chief aim of this work was to increase the oxidative stability of the composite via bulk doping of a matrix with boron, in order to achieve a carbon/carbon (C/C) composite material that will have the same oxidative stability at each point of bulk material. C/C-composite was made of glassy carbon (GC) as a matrix and discontinuous carbon fibers (CF) as a reinforcing component. Oxidative stability of both doped and undoped specimens was investigated by a non-isothermal thermogravimetric analysis. Additionally, oxidative stability of these specimens was investigated in the presence of a catalyst (sodium acetate), which is commonly used as a deicer oil the roads and airports. The observed higher oxidative stability of doped composite in the presence of a catalyst has been discussed, and possible reaction mechanism as an explanation for such a behavior considered.