Pennellia yalaensis, a new species of Brassicaceae from Jujuy Province in Argentina, is described and illustrated, and its phylogenetic relationships with nearest relatives are discussed. This novelty is morphologically related to P. boliviensis and P. brachycarpa, which also grow in the Central Andes of Argentina. However, P. yalaensis clearly differs from both species by the plant height, inflorescence type, and petal length. In addition, trichomes of the basal leaves distinguish the new species from P. boliviensis, and fruit length and number of ovules/seed from P. brachycarpa. Phylogenetic analyses, based on DNA sequences of nuclear ITS and plastid trnL-F regions, confirmed these affinities.