In the context of a taxonomic study of Adesmia ser. Psoraleoides, an endemic group from grasslands in southern Brazil, the new species Adesmia sessilifolia was discovered. This species occurs in a restricted area that represents relictual connections in geomorphology in the South-Brazilian highlands. Adesmia sessilifolia resembles A. paranensis in having glabrous branches and leaves, pilose inflorescences, and arillate seeds, but differs in plant size and in having sessile leaves with apparent veins in both surfaces, as well as in its flowering and fruiting periods and geographic distribution. A description and illustration are provided together with a key for identification of the species of Adesmia ser. Psoraleoides.