The new lichenicolous fungus Capronia suijae growing on the thallus of corticolous Xanthoria parietina is described from Belarus and compared with similar species. In addition to its host selection, the species is characterized by comparatively small ascomata, 40–80 μm diam., and (0–1–)3-septate ascospores, 9·5–11·5×4·0–5·0 μm. A key to the lichenicolous fungi growing on Xanthoria s. str. is provided.