Microsporogenesis and male gametogenesis in Psammosilene tunicoides (Caryophyllaceae) were studied and described for the first time. This species possesses essential embryological features of Caryophyllaceae, such as tetrasporangiate anthers, fibrous endothecium, glandular tapetum, two tapetal cells, simultaneous cytokinesis of pollen mother cells, and three-celled pollen grains. A majority of the microspores were arranged in tetrahedral tetrads, but rhomboidal tetrads were observed in one population. Notable differences in the tapetum degeneration were observed in different populations. Early or late degeneration may both lead to male sterility and subsequently to reproductive failure. The tapetum was dimorphic in two populations. We also included data concerning the breeding system of the species and discussed its implications for conservation purposes.