<p>This review explores the interactions between bivalves and pathogens. It provides a basic description of the most common representatives of different groups of pathogens (viruses, fungi, bacteria, microalgae, protozoa, and metazoa), and the diseases they cause. Among these, <i>Herpes</i> viruses, bacteria of the genus <i>Vibrio,</i> and protozoa of the genera <i>Bonamia</i> and <i>Perkinsus</i> are the most common and harmful threats to mollusk aquaculture. However, even their invasion mechanisms and evasion strategies are still poorly understood. Based on our analysis, we identified five main groups of these mechanisms, including adhesion and colonization factors, inhibitors, toxins, stimulators, and protectors. Our analysis showed that pathogens most frequently use external factors and surface receptor structures that enable communication with host cells, as well as capsules and biofilms that protect the pathogen from phagocytosis. Moreover, the most universal mechanism of invasion is the inhibition of the process of phagocytosis at various stages, as well as the inhibition of reactive oxygen species. An analysis of the literature data showed a lack of knowledge about the mechanisms of pathogen invasion to develop effective technologies to resistance them.</p>