Bleeding and thromboembolism are among the leading causes of mortality worldwide. Thrombosis encompasses both arterial forms—primarily associated with atherosclerosis and leading to heart attacks or strokes—and venous forms. Microvascular thrombosis typically arises in the context of sepsis or systemic inflammation, and it became particularly prominent during the COVID-19 pandemic, substantially contributing to increased mortality. Given this burden, the rapid development of new therapies using advanced techniques and materials to prevent and treat these conditions is essential. This review summarizes recent advances in the design of antithrombotic polymers, discussing mechanisms of action, surface-modification strategies, and current clinical and preclinical applications. It also outlines criteria for evaluating hemocompatibility, describes in vitro and in vivo testing methods, and highlights key barriers to translating these materials into clinical practice. The review concludes by identifying promising directions for future research, including multifunctional approaches that combine antifouling properties, controlled drug release, and bioresistance strategies with the greatest potential to reduce thromboembolic complications associated with medical materials. It further evaluates the progress made to date in combating thrombotic diseases and identifies remaining gaps in the development and clinical implementation of new antithrombotic materials.