Thromboembolism (TE) is an uncommon entity in childhood. Overall 25% of children with thrombosis and more than 40% of children with central venous line (CVL) -related TE enrolled on the Canadian Pediatric Thrombophilia Registry had underlying diagnosis of cancer. However, so far there are very little data describing the epidemiology of TE in children with cancer. Most of the available information in this area originates mainly from retrospective and some prospective observational cohort studies conducted in children with acute lymphoblastic leukemia (ALL). Although ALL has been the most common cancer reported in association with thrombosis in children, available data from small studies indicate that TE is equally common in children with acute myeloid leukemia and lymphoma. TE in association with leukemia and lymphoma seems to be a multifactorial entity. Potential risk factors include increased thrombin generation related to leukemia, age of the patients, use of CVL, chemotherapy including asparaginase and corticosteroids, infections, and inherited prothrombotic state. Management of TE in a child with cancer presents a unique challenge in terms of balancing risk versus benefit. Conservative therapy could lead to clot extension and risks of additional morbidity or mortality; however, chemotherapy-related thrombocytopenia and coagulopathy increase the risk of bleeding complications. In summary, TE is a frequent and serious complication in children with hematologic malignancies. More prospective studies are required to define the epidemiology, pathogenesis, and management of TE in children with hematologic malignancies.