Hematopoietic cell transplantation (HCT) is a potentially curative treatment for children and adults with malignant and non-malignant diseases. Despite increasing survival rates, long-term morbidity following HCT is substantial. Neurocognitive dysfunction is a serious cause of morbidity, yet little is known about neurocognitive dysfunction following HCT. To address this gap, collaborative efforts of the Center for International Blood and Marrow Transplant Research and the European Society for Blood and Marrow Transplantation undertook an expert review of neurocognitive dysfunction following HCT. In this review, we define what constitutes neurocognitive dysfunction, characterize its risk factors and sequelae, describe tools and methods to as...