The park encompasses all state-owned land and water areas owned by the state within the borders of the cooperation area surrounding the park, which is more or less the entire outer archipelago of the Archipelago Sea on the eastern side of the Åland Islands and south of the Korpo, Nagu, Pargas and Kimitoön main islands. The Archipelago Sea Biosphere reserve consists of the national park's cooperation area and the rest of the islands in the Åboland archipelago only accessible by boat or ferry. These areas are mainly situated in Nagu, Korpo, Houtskär, Iniö, Hitis and southern Pargas.