Antarctic terrestrial biodiversity faces multiple threats, from invasive species to climatechange. Yet no large-scale assessments of threat management strategies exist. Applying astructured participatory approach, we demonstrate that existing conservation efforts areinsufficient in a changing world, estimating that 65% (at best 37%, at worst 97%) of nativeterrestrial taxa and land-associated seabirds are likely to decline by 2100 under current tra-jectories. Emperor penguins are identified as the most vulnerable taxon, followed by otherseabirds and dry soil nematodes. We find that implementing 10 key threat managementstrategies in parallel, at an estimated present-day equivalent annual cost of US$23 million, could benefit up to 84% of Antarctic taxa. Climate change is identified as the most pervasivethreat to Antarctic biodiversity and influencing global policy to effectively limit climate changeis the most beneficial conservation strategy. However, minimising impacts of human activi-ties and improved planning and management of new infrastructure projects are cost-effec-tive and will help to minimise regional threats. Simultaneous global and regional efforts arecritical to secure Antarctic biodiversity for future generations.