Cancer-associated thromboembolism (TE) is now a frequent complication in children. The reported prevalence varies from up to 16% of symptomatic to 40% of asymptomatic TE in children with cancer. Compared to the general pediatric population, children with cancer who develop TE have an increased risk of death, TE recurrence, TE-related morbidity and higher potential for utilization of health care resources. TE is preventable with anticoagulation therapy. With over 80% cure rates of childhood cancer, strategies for prevention as well as for early diagnosis and optimal treatment of TE in children with cancer are of major importance. An understanding of the risk factors predisposing children with cancer for development of TE will facilitate development of preventive and therapeutic strategies.