The invasion of alien species manipulates the structure, function, and composition of the recipient ecosystem causing ecological, economic, and social impacts. However, these impacts can be positive or negative, depending on the effect and context of the invasion. In some cases, invasions enhance primary productivity of the ecosystem and increase species richness. On the other hand, in the majority of cases, the invasive species displace native species, adversely impacting native ecosystem and jeopardizing natural resources. The outcome of the impacts is based on several factors, such as mode of introduction, type of invasive species, condition of the invaded habitat, and characteristics of native species. For instance, specialist native species are predicted to suffer adverse effects, while generalists may flourish even when invasive species are abundant. There has been considerable debate in recent times about whether claims of severe impacts of invasive species are exaggerated and whether efforts to manage them are unnecessary or even harmful, and some unintended consequences of invasive species management have been documented. Regardless of the lack of consensus on the impacts of invasive species, they are posing a measurable cost to society. Invasive species severely affect agriculture, fisheries, tourism, forestry, and property values. Countries that rely on agriculture with small landholders are the most vulnerable to the invasion of exotic species. The rate of spread of invasive species is currently surging due to increased travel, trade, and transport in combination with climate change. Accurate and comprehensive information on economic and environmental impacts of invasive species is seriously lacking, and more research is needed to develop management strategies based on the impacts of invasive species.