An unpredecented wave of extinctions is occurring at present, of which human activities are the main culprit. Habitat destruction and invasion by allochthonous organisms are likely the main causes for this loss of biodiversity. Mollusks are one of the main groups involved in these invasions, while likely one of those which has received their main impacts. Therefore, the study of mollusks from this viewpoint allows for a global and more comprehensive understanding of this problem. In this article, some paradigmatic cases of biological invasions by molluscs around the world are discussed.