This study reports on the vascular plant flora inventory of the Nowata County portion of the Oologah Wildlife Management Area in northeastern Oklahoma. A total of 470 species across 305 genera and 95 families were collected. The most species-rich families were Poaceae, Asteraceae, and Fabaceae. 364 species documented in this study had not previously been reported in Nowata County. The inventory provides valuable information on the plant diversity in the area for research, conservation, and management purposes.