Biodiversity conservation requires efficient methods to be integrated into environmental management planning. The Key Biodiversity Area (KBA) approach has been recently developed for identifying sites of greatest conservation importance. They are regarded as priorities for management intervention and for identifying investment priorities. While the KBA approach has been extensively used to identify locations of high biodiversity significance in the terrestrial realm, this methodology is scarcely known by stakeholders in marine jurisdictions. Identification of a network of KBA sites should be regarded as a high priority in diverse and isolated areas, such as oceanic islands. In the Canary Islands (NE Atlantic Ocean), a number of KBA sites are here identified across the archipelago using irreplaceability and vulnerability criteria to safeguard populations of threatened marine species. If global standards associated with the IUCN Red List are considered, only nesting beaches and regular feeding grounds of sea turtles (Caretta caretta and Chelonia mydas) qualify as KBAs. However, this approach overlooks most of the biodiversity hotspots in the Canary archipelago that include representative ecosystems of volcanic islands (e.g. marine caves) or habitats with high conservation importance in terms of productivity, regional rarity and diversity (e.g. seagrass meadows and maërl seabeds), as well as presence of locally threatened species.