Two new species of Platynota are described and illustrated: P. subtinae, new species, from Venezuela, Bolivia, and Paraguay, and P. meridionalis, new species, from Argentina. Although both have been reared only from cotton (Gossypium sp., Malvaceae), they are suspected to be polyphagous, as are nearly all other species in the genus. Two morphological characters of the male genitalia of the new species, i.e., transtilla densely covered with large thorns and juxta deeply excavated in the middle, are most similar to each other and to Platynota stultana Walsingham, described from northwestern Mexico. The two new species are compared to Platynota stultana and P. xylophaea (Meyrick), the latter native to Argentina, with which the new species are superficially similar.