Kosteletzkya C. Presl includes 17 species that are about evenly distributed between Africa and the northern Neotropics. The seven species with known chromosome numbers are exclusively diploid (n  =  19). Here, 47 new chromosome counts are reported and the nomenclature of five of the earlier-counted species is updated. The counts confirm chromosome numbers for six species and provide first counts for eight species. Four of the latter, all African, are tetraploids, and another African species is a hexaploid. Amphi-Atlantic distributions and polyploidy in other malvoid groups are considered. Polyploidy evidence suggests an African origin for the genus.