Oceanic islands are particularly vulnerable to the global decline of biological diversity, suffering disproportionally large losses of endemic species. A primary tool for mitigating species loss is the establishment of protected area networks. The 2030 Global Biodiversity Framework target calls for the protection of 30% of Earth’s land surface by 2030. This study identifies areas within the Tropical Important Plant Areas network of the British Virgin Islands (BVI), to better inform the expansion of the current protected area network with the objective of conserving the BVI’s unique flora. We identified and applied conservation targets for five threatened habitats and 34 species of conservation concern, including four endemic to the BVI. A total of 5,248 georeferenced plant records for the 34 species collected through decades of collaborative work between the National Parks Trust of the Virgin Islands and the Royal Botanical Gardens, Kew, along with the distribution of five threatened habitats were used within the decision support system MARXAN to identify four spatial portfolios to guide the expansion of the BVI’s current protected area network. Highlighting the need to expand the current (2007–2017) Protected Areas System Plan in the BVI, we found that the current Plan only covers 15% of terrestrial land and does not meet the conservation targets for plants and habitats. The portfolios identified in our analysis efficiently expand the current Protected Areas System Plan to strategically expand coverage for all conservation features, with two main portfolios reaching all defined conservation targets for protection. Notably, to evaluate options not requiring land purchase, we extracted areas within state-owned Crown land from two main identified portfolios and found that the two Crown land-portfolios could protect 28% and 23% of the BVI, respectively, while meeting the targets for most plants of conservation concern. However, to reach 30% land protection and meet the conservation targets for all plant species, including endemics, private land would need to be considered for this inclusion within the protected area network. Our results provide science-based guidance for the selection of candidate protected area expansion sites that include threatened plants and habitats for reaching the 2030 Biodiversity Framework targets. While systematic conservation planning can provide guidance on protected area expansion, it is important to evaluate and prioritise conservation actions, based on multiple solutions and available resources. We recommend similar approaches are applied more broadly throughout the Caribbean and other archipelagos across the world.