The kinetic investigation of the solid-state decomposition of a typical melt-spinnable poly[B-(methylamino)borazine] into boron nitride fibers was carried out at various heating rates. It was shown that the two-step weight loss associated with the polymer-to-ceramic conversion is governed by two major diffusion-type transport mechanisms which are independent of the applied heating schedule. The application of the Kissinger and Friedman methods to dynamic TG data allowed us to measure the Ea and lnA values which are seen to increase with the extent of the ceramic conversion from region one (Ea=46.3kJ/mol, lnA=3.85; Friedman method) in going to region two (Ea=122.6J/mol, lnA=12.18; Friedman method). Kissinger and Friedman results are in good agreement. It was shown that the cross-linking process of the polymer is mainly governed by a poorly energetic mechanism indicating the occurrence of simple reactions, whereas the mineralization and ceramization steps are majoritarly represented by a highly energetic mechanism suggesting the occurrence of complex and multi-step mechanisms.