We report previously unrecognized flowering plants of Lao PDR found during a botanical survey of Lao PDR in 2015−2016. We found Phyllagathis tuberosa (C. Hansen) Cellinese & S. S. Renner (Melastomataceae) and Tolypanthus pustulatus Barlow (Loranthaceae) in the Phou Khao Khouay National Biodiversity Conservation Area (PKKNBCA), previously only known from type localities in Thailand. This is the first report of Phyllagathis tuberosa and the genus Tolypanthus in the Lao PDR. We also found Lonicera bournei Hemsl. (Caprifoliaceae) in the proposed Phosabous National Protected Area (PNPA) of Xiangkhoang, neglected with regard to the flora of Laos since its initial report in early 20th century. The current report will augment our understanding of the floristic relationships among SE Asian countries and will help elucidate the biodiversity of Lao PDR.