A morphological analysis of the genus Dennstaedtia (Dennstaedtiaceae) from Argentina is carried out and distributional data updated. The studied species are: Dennstaedtia cicutaria, D. dissecta, D. glauca and D. globulifera. Until now, the information concerning the genus in Argentina was fragmented and incomplete. A comprehensive key to the species and detailed descriptions, distribution maps, habitat considerations, relevant notes, as well as photographs of diagnostic characters are provided for each taxon.