Thrombosis in childhood usually develops secondary to underlying causes. One of the most important risk factors is cancer. It has been reported that the incidence of thrombosis in children with cancer is 2-16% when symptomatic thrombosis is mentioned and it climbs up to 50% if asymptomatic conditions are included. Thrombosis associated with childhood cancers is multifactorial. In addition to the prothrombotic effect of cancer, mass effect, vascular invasion of cancer, drugs used (e.g., steroid, asparaginase), catheter, infection, immobilization, surgery, total parenteral nutrition, and comorbid genetic thrombophilia are the most important underlying etiologies. Thrombosis can cause morbidity, mortality, as well as inadequate or delayed treatment. Among childhood cancers, thrombosis risk is more common in acute lymphoblastic leukemia and lymphoma than in solid malignancies. Among the drugs used for the treatment of thrombosis, low molecular weight heparin constitutes the most important group. Warfarin, on the other hand, can be preferred in case of long-term use, but its use may be challenging due to polypharmacy and nutritional instability on warfarin efficiency. Thrombolytic therapies are rarely used in selected cases. In addition to general measures to reduce the risk of thrombosis, prophylaxis is controversial. Prophylaxis has not been included in the standard guidelines for the prevention of thromboembolic complications in childhood. It can be considered for use in high-risk patients. However, prophylaxis during cancer treatment may be more challenging, especially in this group of patients who need frequent interventions (e.g., intrathecal treatments) and have an increased risk of bleeding secondary to thrombocytopenia and coagulopathies. There are many continuing studies on the prophylactic and therapeutic use of new-generation anticoagulants in childhood.