The knowledge about terrestrial diatom assemblages in southern Africa is rather limited, despite a long history of diatom research in this area. Terrestrial habitats are places of characteristic diatom floras, dominated by species resistant to desiccation which are able to thrive in conditions of limited water availability. The presented work expands the knowledge about these unique habitats. During the study on terrestrial moss-inhabiting diatoms from Western Cape Province (South Africa), four taxa with a unique set of valve features have been found and described herein as new species, based on light and scanning electron microscopy. These new species are: Luticola microcephala M. Rybak, Peszek & Kochman-Kędziora, sp. nov., Luticola asymmetrica M. Rybak, Kochman-Kędziora & Peszek, sp. nov., Luticola terrestris Kochman-Kędziora, M. Rybak & Peszek, sp. nov. and Microcostatus meridionalis Peszek, M. Rybak & Kochman-Kędziora, sp. nov. Algal community composition had low species richness (9–15 taxa per sample) and samples were dominated by: Humidophila contenta , Nitzschia brevissima and Eunotia aff. pseudominor . The three new Luticola species formed numerous populations, exceeding 10% of the share, whereas Microcostatus meridionalis reached 5.4%. Basic morphological data of associated diatom flora together with detailed micrographs are also provided.