Pump thrombosis is a specific cause of major left ventricular assist device dysfunction associated with an increased risk of significant morbidity and mortality, often requiring emergent medical or surgical intervention, including device exchange or heart transplantation. Given the clinical significance of pump thrombosis, much of the advancement in device technology over the last two decades has been focused on improving design and functionality to reduce the risk of thrombosis and subsequent device malfunction. In this chapter, we discuss a historical perspective of LVAD pump thrombosis, from first-generation pulsatile flow devices to axial and magnetically levitated continuous-flow devices. We also discuss the pathophysiology of and risk factors for pump thrombosis, its incidence across devices, the prevention, detection, and management of acute pump thrombosis, and the current state of outcomes following this complication.