A new species of the previously monotypic xanthid genus Crosnierius Serène & Vadon, 1981 is described from the South China Sea. The species differs from Crosnierius carinatus Serène & Vadon, 1981 in the structure of the anterolateral teeth, ambulatory leg proportions and form of the male first pleopod. Paramedaeus planifrons (Sakai, 1965) is also reported from the South China Sea, the first record of the species outside its type locality of Japan.