The Anthropocene is characterised by a continuous human‐mediated reshuffling of the distributions of species globally. Both intentional and unintentional introductions have resulted in numerous species being translocated beyond their native ranges, often leading to their establishment and subsequent spread – a process referred to as biological invasion. Biological invasions are associated with profound changes in the composition, structure, and functioning of recipient ecosystems, plus substantial financial losses and disruptions to society, culture, and human well‐being. These ecological, economic, and socio‐cultural impacts are interrelated, ubiquitous, and detrimental, yet they are often subjectively perceived or inaccurately quantified. Persistent knowledge gaps remain, however, which limit our understanding of the complex and multifaceted causes and mechanisms of invasion impacts. To overcome these gaps and comprehensively capture all related facets pertaining to the nature and diversity of invasion impact, this scoping review of academic studies, grey literature, and expert reports provides a conceptual model for interpreting invasion impacts, structured around three interrelated pillars: impact domains, challenges in the study of impacts, and available risk‐ and impact assessments. We initially explore the various mechanisms and consequences of ecological, economic, and socio‐cultural invasion impacts and their temporal dynamics, substantiating these with relevant empirical examples. We then review common challenges and fallacies in studying invasion impacts, including context specificity and inter‐comparability of impact magnitudes, challenges associated with quantifying non‐ecological impacts, and research biases, before synthesising how risks are analysed and impacts assessed, and how these assessments ultimately inform management decisions. Our review underscores the multifaceted and complex nature of invasion impacts, and that effectively addressing biological invasions requires more than isolated, reactive interventions; it calls for globally coordinated, proactive action underpinned by reliable scientific knowledge, sincere political commitment, and broad public engagement. Drawing on nearly a century of literature and global expert contributions, this work offers a comprehensive, nuanced, and timely overview of the potential consequences of biological invasions, providing a valuable foundation for informing future research directions, management interventions, and policy development.

Extensive invasion of Ponto–Caspian gobies raised the question how they affect recipient ecosystems. The round and racer goby pose a threat to their native counterparts, cottid species, but the influence of other gobiids is still not sufficiently demonstrated. We experimentally assessed how monkey and western tubenose goby, two of the most widespread species across Central and Western Europe, affected time spent by bullhead in the shelter in different seasons and light conditions. Direct and indirect aggression and guarding the shelter by the fish were also checked. We observed the behaviour of single-species and mixed-species pairs in the presence of a single shelter, with bullhead as a resident and one of three species as an intruder introduced to the tank 24 h later. Neither tubenose nor monkey goby was the stronger competitor, capable of outcompeting bullhead from the shelter. Their influence on the resident bullhead was the same as that of intruding bullhead: all intruders made resident bullhead increase shelter occupancy in spring at night. Moreover, compared to the monkey goby, the tubenose goby spent more time in the shelter, occupied it similarly in both seasons, guarded it more intensely and was more aggressive. The monkey goby displayed indirect aggression more often in spring. Despite these differences, bullhead responded to the presence of both goby species similarly, especially during reproductive season.