Basidiocarps of an undescribed dacrymycetous species were collected from Pinus densiflora forests in Japan and described as a new species, Femsjonia uniseptata, based on both morphological characteristics and phylogenetic analysis. This new species is characterized by having discoid to applanate basidiocarps with white hairs at the margins; thin-walled internal and marginal hyphae with clamp connections; and 0–1-septate basidiospores. A detailed description, line drawings, phylogenetic tree to show the placement of F. uniseptata and comparison of the new species with allied taxa are provided.