Information on 45 vascular plant species new for the Kizhsky Federal Zoological Reserve is provided. Regionally red-listed Gymnocarpium robertianum and Moehringia lateriflora, as well as native Lathyrus maritimus and alien Primula veris were discovered for the first time in Zaonezhye at large. Among the new species, 27 are adventitious, and most of them are widespread in Karelia and inhabit various secondary habitats (Alchemilla micans, Juncus compressus, Lamium dissectum, Poa compressa, Senecio vulgaris, Spergularia rubra). At the same time, introduced species that are very rare and known from very few localities (Alchemilla conglobata, Armoracia rusticana, Papaver pseudoorientale, etc.) have also been recorded. Most of the alien species grow on Kizhi Island, whose ecosystems are affected by significant anthropogenic pressure, which is responsible for their accidental introductions, or escape from places of cultivation. Several aggressive adventitious species (Epilobium pseudorubescens, Impatiens glandulifera, Lupinus polyphyllus), which have been actively invading the natural and seminatural communities in the republic over the past decades, have been recorded here, too. Some popular and widely cultivated garden and ornamental plants (Dianthus barbatus, Lycopersicon esculentum, Malus domestica, Papaver somniferum, Saponaria officinalis, etc.) were noted. For five species (Cypripedium calceolus, Isoëtes echinospora, Hypopity monotropa, Lobelia dortmanna, Neottia nidus-avis) that are red-listed in Karelia and/or in the Russian Federation, new locations are stated.