Nano-crystalline boron doped silicon carbonitrides were produced from polymers with the chemical composition (B[C₂H₄–Si(CH₃)NH]₃)_n and investigated for their high temperature mechanical properties. Compression creep experiments in the temperature regime of 1350–1500 °C, coupled with constant loads between 25 MPa and 150 MPa were carried out in atmospheric ambience. Electron microscopic studies indicated oxidation induced secondary and tertiary stages of creep behavior for the first time which was not reported for these classes of ceramics earlier. Extensive oxidation with temperature and time progressively transformed the highly covalent non-oxidic microstructure to that of a low viscous oxidic one, albeit high creep resistance exhibited by these materials at extreme conditions of creep.