Summary: Astragalus argaeus Boiss. & Balansa is a single locality, endemic species belonging to the monotypic Sect. Argaeus. In this study, morphology, ecology, pollen, legume and seed properties of the species have been examined. An amended and complete morphological description of the species is provided, and the conservation status and potential threats are evaluated. © 2012 The Board of Trustees of the Royal Botanic Gardens, Kew.