Thrombocytopenia in cancer patients is a multifactorial condition that requires careful monitoring and management. Understanding the underlying mechanisms and implementing appropriate treatment strategies are essential for improving patient outcomes. In cancer patients, thrombocytopenia can be caused by several factors, including direct cancer bone marrow invasion, chemotherapy-induced myelosuppression, microangiopathic disorders, and immune disorders. The occurrence of thrombocytopenia complicates the management of malignant disease, as it increases the risk of bleeding during surgical procedures, invasive diagnostic procedures, and even routine activities and health-related quality of life. Management strategies include platelet transfusions, dose and time adjustments of chemotherapy regimens, administration of thrombopoietin-receptor agonists (TPO-Ras), hitting underlying causes, and managing more complex conditions such as immune thrombocytopenic purpura (ITP) or disseminated intravascular coagulation (DIC). In this context, particularly challenging is the condition of thrombocytopenic cancer patients who need anticoagulant or antiplatelet treatments for concomitant cardiovascular disorders. In these cases, a careful balance between thrombosis and bleeding is required. This chapter will explore the key aspects of thrombocytopenia in cancer patients, including the leading causes, epidemiology, and management strategies. It will also highlight the relevance of thrombocytopenia in cancer patients receiving antithrombotic treatments for any indication.