Silicon oxycarbide (SiOC) is a promising protective coating material. However, so far there has not been any comprehensive review to systematically evaluate the characteristics and properties of this material as coatings. In this review, SiOC compositions and fillers are examined based on their fundamental functions in the coating materials. From a processing point of view, different coating formation processes, such as plasma-enhanced chemical vapour deposition, dip coating, and spin coating, are discussed. As an intrinsic requirement and one of the most challenging aspects for SiOC to be used as coating materials, the stability of SiOC in air conditions is analysed and the degradation mechanisms of SiOC are discussed. Lastly, for different application needs, the physical and mechanical behaviours, electrical conductivity, and optical property of the coatings are presented. This first-ever systematic review on the SiOC system as coating materials is intended to provide guidance for future SiOC coating development.