We discuss nomenclatural and taxonomic matters pertaining to three species of Cyperus subg. Diclidium (Schrad. ex Nees) C. B. Clarke, viz., C. acicularis (Schrad. ex Nees) Steud., C. flexuosus Vahl, and C. macrocephalus Liebm. We examined the relevant available type materials of the three species and their associated synonyms. Our study shows that based on priority, the names C. ferax Rich. and C. conglobatus Link replace C. flexuosus and C. macrocephalus, respectively. For C. acicularis, a later homonym (non (L.) With.), C. strongii G.C. Tucker & Gandhi is proposed as the replacement name. A key is provided for identification of all the Cyperus subg. Diclidium species occurring in the New World.