SiC nanowires (NWs) with diameters of 20–200 nm and lengths from tens to hundreds of micrometers have been synthesized by the carbothermal reduction of colloidal silica. The morphology and microstructure of NWs have been studied in detail by electron microscopy techniques. SiC NWs have been found to be hexagonal prisms, “bamboo-like” nanorods and nanobelts. The NWs with a [111] growth axis are hexagonal prism nanorods, while the nanobelts have growth directions varying from [110] to [113]. It has been found that NW growth proceeds in two stages. Initially, SiC crystallites grow on the carbon fiber surface. These crystallites serve as seeds, on which the SiC NWs nucleate and grow. The crystallites containing microtwins and stacking faults (SFs) with a preferential [111] growth direction give rise to the growth of nanorods, while the nanobelts start growing on the (111) facets of relatively perfect crystallites. Wires with core (SiC)–shell (SiO₂) structure have been obtained under special temperature treatment in air. The core–shell structure has been confirmed by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) mapping techniques.