A new species, Vernonia occulta (Asteraceae, Vernonieae), from the state of Oaxaca, Mexico is described. The new taxon is distinguished from Vernonia cronquistii, which is also distributed in this region, by fewer florets per head, linear-lanceolate leaves, and different leaf trichomes: the new taxon has uniseriate trichomes with four to six basal cells and one subulate apical cell, while V. cronquistii has lageniform trichomes. We also include an artificial identification key to the Mexican species of the genus Vernonia s. s.