Venous thromboembolism (VTE) is a major cause of death in cancer patients, second only to malignancy itself. It is a common complication and is often underestimated. On average, one out of every three people with cancer will suffer from thromboembolic events, which can significantly impact their quality of life, decrease life expectancy, and increase their vulnerability. Extensive clinical studies have been conducted over the years to determine the best prophylaxis and treatment strategies for venous thromboembolism in cancer patients, who are at a high risk of thrombosis and bleeding compared to the general population. These studies have resulted in dedicated international guidelines for managing this condition in various medical and surgical settings. Despite advances in cancer treatment, managing the cardiovascular health of cancer patients remains a complex issue. This is due to the individual variability of each patient's medical history and cardiovascular risk factors, as well as the type, location, and stage of their cancer, and the use of novel anticancer drugs. This chapter aims to highlight key observations in cancer and thrombosis, from tumor biology to clinical trials of anticoagulants.