We report 14 species of flowering plants as new additions to the flora of Laos. These are Illex viridis (Aquifoliaceae), Capparis erycibe (Capparaceae), Euphorbia bokorensis (Euphorbiaceae), Exacum darae (Gentianaceae), Aeschynanthus cambodiensis (Gesneriaceae), Tetraphyllum roseum (Gesneriaceae), Utricularia gibba (Lentibulariaceae), Macrosolen brandisianus (Loranthaceae), Decaschistia siamensis (Malvaceae), Nyssa yunnanensis (Nyssaceae), Adenia penangiana var. penangiana (Passifloraceae), Pentaphylax euryoides (Pentaphylacaceae), Wikstroemia bokorensis (Thymelaeaceae), and Debregeasia wallichiana (Urticaceae). We discovered the species during a botanical survey of the Phou Khao Khouay National Biodiversity Conservation Area (PKKNBCA) of Lao PDR in 2015-2019. In addition, nine rarely collected flowering plant species in Laos are newly reported for the PKKNBCA.