Based on sequences of ITS, matK, rbcL and rps16, a phylogenetic tree is constructed for Pseudostellaria and outgroup genera of Caryophyllaceae subfamily Alsinoideae including Stellaria and Cerastium, and members of subfamily Caryophylloideae, by means of maximum parsimony, maximum likelihood and Bayesian inference. The results indicate that core Pseudostellaria is monophyletic; however, the presence of two recognizable clades in the genus does not support the current infrageneric classification into two sections. Evolution of six morphological characters, including root tubers, stamen number and cleistogamous and chasmogamous flowers, reflect phylogenetic relationships between Pseudostellaria and allied taxa. The three North American Pseudostellaria spp. fell outside of the genus; Pseudostellaria sierrae and Pseudostellaria oxyphylla formed a well-supported clade, and they are treated as a new genus, Hartmaniella.