A new milkweed from the eastern and western cordilleras of Mexico is described and illustrated. Asclepias elegantula Fishbein is distinguished from other diminutive, linear-leaved species of the genus in montane Mexico by the claret-striped petals (unique in American Asclepias L.) and by the combination of very small flowers with corona segments (hoods) that are sharply deflexed from the staminal column, deeply pouched, and bear a grooved, internal appendage (horn) confluent with the dorsal margin of each hood. The species is known from only two sites with different substrates, one each in the Sierra Madre Oriental and Sierra Madre Occidental. The remarkable disjunction may be indicative of extreme rarity or the low likelihood of observing this relatively inconspicuous milkweed.