Zwackhiomyces cervinae Calat., Triebel & Pérez-Ortega is described as new to science from Spain and Iran. This lichenicolous species grows on the lateral side of the squamules of Acarospora cervina, and it is characterized by its relatively large ascospores, which are brown when overmature. It is compared with several Zwackhiomyces species and with other taxa sharing some of its characters. A key to all the known species of the genus is also provided.