This dataset contain inventories of the impacts of invasive alien species (IAS) in Brazil, Chile, and Argentina. These include seven case studies: pines (Pinus contorta) in the Araucanía and Aysén Regions (Chile); (ii) pines (Pinus contorta) in the Northern Patagonia Region (Argentina); (iii) privet (Ligustrum lucidum) in the Yungas Forest (Argentina); (iv) invasive grasses (Urochloa brizantha and Urochloa decumbens) in the Cerrado (Brazil); (v) the American mink (Neovison vison) in Austral Patagonia (Argentina); (vi) the American mink in the Los Ríos Region (Chile); and, (vi) the yellow jacket wasps (Vespula germanica) in the Los Ríos Region (Chile). The impacts were elicited by experts (varying between two and four experts for each case study) following the procedures described in the supporting files. A total of 1,526 impacts were identified by the experts, and these impacts can be found in the "Compiled-Impact.csv" file. This file contains information about the impact outcome, impact mechanism, EICAT impact category, level of confidence, the species or asset impacted, the direction of the impact, the extent of the study area, the name of the IAS, whether the IAS is a plant or an animal, and the country. After two rounds of scoring, the impacts listed in the “Compiled-Impact.csv” were further discussed during a facilitated workshop in San Carlos de Bariloche (Argentina; December 2019). The final, agreed impact scores can be found in the file "Unique-Impact.csv". This final dataset contains 209 impacts and information about the same variables described above for the "Compiled-Impact.csv" file. Full details about this dataset can be found at https://doi.org/10.5285/d00a647a-16ec-4d2a-a3a3-ad59597e8ca2