The structural evolution of SiC precursors prepared from tetramethoxysilane (TMOS) and phenol resin by H 2O polymerization and heat-treated between 80 and 1400 °C was investigated by X-ray diffractometry (XRD), large-angle X-ray scattering (LAXS), transmission electron microscopy (TEM), and by 29Si and 13C nuclear magnetic resonance spectroscopy (NMR). After hydrolysis and drying at about 80 °C, the samples structurally consist of domains of partially hydrogenated silica and of coexisting phenol resin. Heat-treatments carried out on the predried material yield different stages of structural evolution, though the precursor is non-crystalline throughout the whole temperature field investigated: • — Stage I (≤ 500 °C): gradual temperature-dependent decomposition of phenol resin and simultaneous dehydrolysis of silica. • — Stage II (≥ 500–≤ 1400 °C): breakdown of the local structural order of phenol resin and formation of C domains with graphite-type short-range-order. C coexists with non-crystalline SiO 2 containing low amounts of OH-groups. The C and SiO 2 domains up to ≈ 1000 °C are extremely small (≤ 1 nm). At higher temperatures, C and SiO 2 domains become larger (≈ 2–3 nm at 1400 °C) and develop partial ordering of the short-range structure.