Venous thromboembolism (VTE) is the second most common cause of mortality in cancer patients and also points towards unfavourable prognosis. In about 10% of patients with idiopathic VTE there is underlying malignancy. However, the efficacy of extensive tumour screening in those patients is not yet established. Numerous plasmatic and cellular components contribute to the phenomenon of hypercoagulability in cancer patients, including Cancer Procoagulant and activation of coagulation with high levels of coagulation factors. Cancer surgery carries an increased risk compared to non-cancer patients necessating more intensive and longer thromboprophylaxis in those patients. In medical patients active cancer is associated with increased risk for VTE. In the treatment of VTE, cancer patients have a significantly higher recurrence rate for VTE when treated with vitamin K-antagonists (VKA) compared to non-cancer patients. Compared to VKA the use of low molecular weight heparin for long-term secondary prevention is more effective than vitamin K-antagonists. Thus, there is a grade 1A recommendation to use low molecular weight heparin for cancer patients during the first 3-6 months of secondary prevention of VTE. Several studies indicate that low molecular weight heparin may also improve the prognosis of cancer patients quoad vitam, particularly for cancer patients at an earlier stage of disease; this needs to be confirmed in further studies.