A taxonomic synopsis of Klasea Cass. sect. Schumeria (Iljin) L. Martins (Asteraceae, Cardueae) is presented. One new species, K. khorasanica Ranjbar & Negaresh, collected from Khorasan Province in northeastern Iran, is described and illustrated. Serratula calcarea Mozaff. is transferred here as K. calcarea (Mozaff.) Ranjbar & Negaresh. Also transferred from Serratula L. is K. litwinowii (Iljin) Ranjbar & Negaresh [≡ S. litwinowii Iljin], which is lectotypified with an emended description. The two species are closely related to K. latifolia (Boiss.) L. Martins, lectotypified herein, and characters to distinguish these species are given. A description of Klasea sect. Schumeria, an enumeration, and a taxonomic key to its 10 species are provided. The name K. viciifolia (Boiss. & Hausskn.) L. Martins [≡ S. viciifolia Boiss. & Hausskn.] is lectotypified in recognition of Rechinger's 1980 (ined., “type”) sheet annotation.