The electrical conductivity of a layered mullite-sialon-silicon carbide composite has been studied using impedance spectroscopy. The combination of particles (mullite-sialon) and fibres (sialon-SiC) was thought to pose interesting electrical behaviour. The Nyquist plots of complex impedance have been obtained the deconvolution of which indicate an equivalent circuit with an element of constant phase. The Bode plots showed that two relaxation processes are present with two different activation energies (bulk and intergranular). This implies that the conduction process is thermally activated in the composite and activation energies are reported. These results were found to be significantly higher than those obtained for the composite obtained by the same processing route completely oxidised. It is concluded that the electrical conductivity differences of both partially and fully oxidised composites can easily and accurately be monitored by impedance spectroscopy.