Two extinct species of balanomorph barnacles are identified from the La Meseta Formation (Eocene) of Seymour Island, Antarctic Peninsula. The report of Austrobalanus macdonaldensis Buckeridge in subunits Telm 5 and 7 represents the first noted occurrence of the species outside of South Island, New Zealand, and the first record of the genus Austrobalanus Pilsbry outside of Australasia. The notice of Solidobalanus sp. in subunits Telm 2, 5, and 7 represents the earliest known occurrence of the genus in the Southern Hemisphere. Records of the genus from middle Eocene deposits in Western Europe and North America predate those from the La Meseta Formation. Each taxon is typically associated with subtidal and inner shelf faunal assemblages in moderate- to high-energy environments.