Abstract: 1. Alien species can be damaging to native biodiversity, human well-being and the economy. Identifying the complete range of impacts they cause, and the ways that these impacts are connected, may inform the prioritisation of management actions to mitigate impacts. 2. Using datasets on the biodiversity impacts and monetary costs (damage and management costs) of alien birds, we aimed to establish whether species with the most severe biodiversity impacts also had the highest costs; whether types of biodiversity impact were associated with high costs; and whether specific factors associated with alien species are linked to both damaging biodiversity impacts and high costs. 3. We identified a positive relationship between a specific type of biodiversity impact (predation) and costs, possibly because predation by alien birds can be severely damaging to native species and therefore attracts management actions. However, predation impacts are likely to occur more frequently and to be easier to identify than some other impact mechanisms such as hybridisation and transmission of diseases, and they are therefore likely to be more frequently managed and hence to have costs. 4. We identified a specific species characteristic (generalism) to be associated with severe biodiversity impacts and high costs, probably because generalist species have greater opportunity to cause impacts, whether they be on biodiversity or the economy, or both. We also found widely distributed alien birds to be associated with high costs, probably because these species also have greater opportunity to cause impacts. 5. Management interventions that prevent the introduction of both predatory and generalist alien bird species, or that reduce their geographic distribution at early stages of invasions, may have significant biodiversity and economic benefits. Plain Language Summary: https://relationalthinkingblog.com/2023/07/18/plain-language-summary-linking-the-biodiversity-impacts-and-monetary-costs-of-alien-birds