A polysilane (PS) has been modified chemically with aluminium acetylacetonate (AlAce) to prepare new Si‐Al‐C‐O precursors. Chemical reactions occur between PS and AlAce and this gives rise to higher pyrolysis yields from the precursors at 900°C in nitrogen, compared with that of PS, due to network formation by crosslinking. Further pyrolysis of the precursors to 1700°C in nitrogen produces ceramics of the SiC‐AlN system with composition dependent on the AlAce/PS ratio. The structures of the precursors and their pyrolysis products have been characterized and the influence of the AlAce/PS ratio has been elucidated.