Silicon oxynitride ( Si 2 N 2 O ) nanowires (NWs) were grown in situ on the cell walls of silicon carbide and alumina foams by coating preceramic polymers containing a Co-based catalyst, followed by pyrolysis in nitrogen at temperatures ranging from 1250°C to 1450°C. The relationship between different processing factors (type of substrate and preceramic polymer, pyrolysis temperature) and the growth of NWs was examined. Varying processing factors were found to be effective for controlling the growth of NWs. The use of a preceramic polymer containing a high amount of carbon as well as silica impurities present in the SiC foams led to a larger amount of longer NWs, homogeneously covering the ceramic struts of the porous substrates. The overall morphology and growing mechanism of the NWs on ceramic foams were investigated.