In 2021 we conducted a botanical inventory of Agguttinni Territorial Park, a large (16,465 km2) new protected area on the east-central coast of Baffin Island in Nunavut, Canada.  The park stretches from the Barnes Ice Cap to Baffin Bay and encompasses ice-capped mountains and deep fiords up to 120 km long. Previous knowledge of the plant and lichen biodiversity was very limited and based mostly on collections made during the 1950 Baffin Island Expedition.  Based on our 2021 collections and those by other botanists, we documented a comprehensive park vascular plant flora of 141 species (3 with 2 subspp. each) of vascular plants belonging to 25 families. Although not the focus of our 2021 inventory, our preliminary list of bryophytes includes 69 species belonging to 27 families, and of lichens includes 95 species (1 with 2 subspp.).  All species are native; no introduced species were recorded. The majority of vascular plant and bryophyte species are newly reported for the park area. The largest vascular plant families are Poaceae (22 spp., 1 with 2 subsp.), Cyperaceae (22 spp.), and Caryophyllaceae (15 spp.), and the largest genus is Carex (16 spp.).  Noteworthy records include the northernmost records of Diapensia lapponica in Canada and the first record of Puccinellia bruggemannii from Baffin Island. Our bryophyte list for the park includes 7 taxa newly reported for Nunavut. One rare lichen was documented: Parmelia skultii, which appears to be new to Baffin Island. Vascular plant species diversity varied greatly among localities within the park, with inland valleys at the heads of fiords the most diverse (up to 107 spp.) and interior rocky barrens the least diverse ( < 1 0 spp).