Canopy-forming algae are important habitat providers in coastal ecosystems. Several canopy-forming species have spread outside their native geographic range. We investigated the role that these invasive non-native algae play in providing habitat for meiofaunal species. Sargassum muticum is a native species in East Asia and has been a successful invasive species of North American and European coasts. The nematode assemblages living in intertidal S. muticum on the English Channel coast in Europe, where it is an invasive species, were compared to those within its native range on the southern coasts of Korea. Nematode assemblages were sampled using a nested survey design (replicates nested within patches within shores within regions within coastlines in each country). Significant differences between countries were found in nematode assemblages in terms of both taxonomic composition and functional traits. Despite differences in assemblage structures between countries, some cosmopolitan nematode species were present in both countries. These nematode species may possibly have come from Asia to Europe with S. muticum.