Schlechteranthus subgenus Microphyllus is a recently erected subgenus, which is revised here for the first time. The subgenus is comprised of nine succulent species, including a new species S. parvus, and are endemic to the arid part of the Greater Cape Floristic Region. Schlechteranthus subgenus Microphyllus can be distinguished from subgenus Schlechteranthus by the smaller leaves (3.5-5.0 × 4-6 mm vs. 5-30 × 3.5-9.0 mm) and smaller capsules (2-6 × 2-6 mm vs. 6-11 × 4-9 mm), with seven to nine locules and small closing bodies that block one third of the locule (vs. 10 to 12 locules and closing bodies that block three quarters of the locule). Differences in leaf shape, degree of fusion, and arrangement, as well as inflorescence and spine structure were identified as important characters in distinguishing species in the subgenus. Schlechteranthus parvus, S. pungens, S. spinescens, and S. stylosus all share the presence of spines, caducous bracteoles, and cymose inflorescences. Maps illustrating species richness hotspots within a quarter degree square were produced for the genus and subgenera respectively. A key to the subgenera in Schlechteranthus and a comprehensive taxonomic treatment of subgenus Microphyllus is presented, including a key to the species, descriptions, figures illustrating diagnostic characters and distribution maps.