The manner in which a series of silcarboranylene–siloxane polymers behave in air at elevated temperatures was investigated by thermogravimetric, isothermogravimetric, and differential thermal analyses techniques. Results indicate that methyl pendant groups on the polymers undergo thermal and oxidative degradations at temperatures under 600°C. Final weight losses of the polymers, however, are significantly lower than that shown by dimethylsiloxanes. The reduced volatility is attributed to the inhibition of thermooxidation by the m-carboranylene group in the polymer molecules. This protective influence decreases apparently as the distance between the carborane nucleus and the methyl groups increases.