Baffin Island in the eastern Canadian Arctic is the largest island in Canada and the fifth largest in the world. East-central Baffin Island, a spectacular mountainous area covering over 57,000 km2, with long fiords, deep U-shaped valleys, glaciers, and icecaps, is one of the least botanically collected and documented areas of the island. Here, we report the results of a floristic study of vascular plant diversity in east-central Baffin Island based on historical and recent collections and field studies. Previous published accounts covering the flora area cited no or few voucher collections. We compiled a dataset of 3,206 unique collections made between the 1860s and 2022, including 850 collected by us. The vascular plant flora comprises 26 families, 71 genera, 163 species (4 with two subspecies each), and 2 nothospecies. The six most species-rich families are Cyperaceae (26 species), Poaceae (24), Brassicaceae (16), Caryophyllaceae (15), Saxifragaceae (11), and Asteraceae (11). The largest genera are Carex (19 species), Draba (9), Potentilla (8), and Saxifraga (8). More than half of the taxa are circumpolar in distribution, few are restricted to North America, and none are endemic to Baffin Island. All taxa found in east-central Baffin Island are native. Many taxa appear to be rare in the flora area; 33 are known from only 1–3 collections and 45 from only one or two localities. Remarkably high diversity was recorded in valleys at the heads of fiords, accounting for 94% of the total flora, which may be attributed to a warmer climate along with high habitat diversity. We document 21 taxa new to the flora area. Particularly noteworthy records include Puccinellia bruggemannii, newly reported from Baffin Island; Ranunculus sabinei and Crucihimalaya bursifolia, not known elsewhere on Baffin Island and disjunct by over 1,000 and 500 km, respectively; Carex holostoma, Diapensia lapponica, Harrimanella hypnoides, and Vaccinium vitis-idaea, northernmost records for Canada; and Arctous alpina and Ranunculus trichophyllus, northernmost records for eastern Canada. Our data show that species new to the flora area continue to be reported and that vast areas within it are botanically under-explored, so we expect that future work will further expand our understanding of the flora of east-central Baffin Island. This study provides essential baseline data for monitoring the impacts of climate change on the flora of this Arctic region.