Microstructure, oxidation behaviour, and electrical and mechanical properties of quasi-carbon fibre-reinforced quasi-carbon matrix (QC/QC) composites were investigated. The composite was prepared by heat treating a QC fibre or OXPAN fibre-reinforced polymer matrix composite at a temperature of 500 °C. Different polymer precursors have resulted in the QC/QC composites with varying thermal behaviour. The phenolic matrix derived QC/QC composites followed a self-acceleration mechanism and had better oxidation resistance than the polyacrylonitrile (PAN) matrix-derived QC/QC composites. Because of fewer chemical reactions involved in the pyrolysis process, the QC/QC composites obtained from QC fibre-reinforced composite precursors exhibited higher flexural modulus and strength and were superior to those derived from oxidized PAN (OXPAN) fibre-reinforced composite precursors. Unique semiconducting and switching characteristics have been observed in the QC/QC composites, which would make them promising for electronic device applications.