The objective of this study was to collect and document the vascular plant species at the 2236-ha Brookhaven National Laboratory. We made collecting trips at 2-week intervals from April 2007 to October 2009 during which we identified 320 species in 226 genera in 98 families. The Asteraceae (45 species) and Cyperaceae (24 species) were the most commonly collected families. The most diverse genera were Carex spp. (sedges) and Quercus (oaks) with 11 and 9 species, respectively. One hundred eight species, 34% of the flora, were non-native taxa. We observed 2 rare taxa at the study site: Lespedeza angustifolia (Narrowleaf Lespedeza) and Rhynchospora scirpoides (Longbeak Beaksedge).