The taxonomic richness of the marine Nematoda in coastal habitats of Brazil and similarities in generic composition among them are analysed. A complete faunal list is presented, containing 11 orders, 59 families, 294 genera and 231 species, among which 1 family, 10 genera and 87 species were discovered for the first time in Brazil. Seven habitats were considered (sandy beaches, estuaries, phytal, oceanic islands, beach rocks, salt works and artificial substrates): sandy beaches had the greatest generic richness (241), followed by estuaries (142) and the phytal environment (126). Taxonomic composition was similar to that of other coastal habitats sampled worldwide, with Chromadoridae and Xyalidae the most representative families. The three major habitats (beaches, rocky shores and estuaries), showed statistically significant differences in faunas. Estuaries were the most uniform in composition.