Four new species of Isidrogalvia (Tofieldiaceae) from sandstone massifs on the Guiana Shield are described, illustrated, and their morphology compared to other species. Isidrogalvia sipapoensis and I. penduliflora are unusual in the genus in having pendant flowers. Isidrogalvia penduliflora, I. neblinae, and I. paniculata are relatively robust species endemic to Cerro de la Neblina. The last is unique in Tofieldiaceae in having a compound inflorescence. A bilingual key (English-Spanish) to the six species of Isidrogalvia occurring in the Guayana Highlands is provided. The morphology and familial placement of Isidrogalvia are discussed.