Paxillus, a type of ectomycorrhizal fungi distributed widely in the world, is also an essential category for researching bioactive substances and pharmacological functions. We discovered fruitbodies of Paxillus involutus covered in a layer of white mycelium in 2020. Cladobotryum verticillatum, a pathogenic fungus related to cobweb disease, was isolated and identified based on morphological and phylogenetic features. Koch's postulates were used to confirm the pathogenicity. The host range test revealed that C. verticillatum could cause disease in all examined mushrooms except Ganoderma sichuanense. To our knowledge, C. verticillatum is a new record species in China and a new pathogen on Paxillus involutus.