Based on thin plate/elastic foundation theory and strain energy release rate calculations, this paper presents a lateral crack model to analyse the threshold for and development of impact damage in brittle coatings. Numerical solutions indicate that an increase in coating-to-substrate elastic modulus ratio tends to enhance the coating’s resistance to impact damage initiation. The size of the lateral crack in a coating layer is a function of the coating thickness. For comparison with the theoretical prediction, experiments were performed on SiC-coated graphite specimens, as well as on glass microscope slides resting on various kinds of substrates.