Background: Cancer patients represent an at-risk population for Venous Thromboembolic Events (VTE). Our study aimed to evaluate the impact of VTE on the length and cost of hospital stay in French patients hospitalized for breast cancer (BC), colon cancer (CC), lung cancer (LC) or prostate cancer (PC). Methods: The French national hospital database (PMSI) and the disease-specific ICD-10 codes were used to identify BC, CC, LC or PC patients diagnosed in 2010 who were hospitalized with a VTE during the following two years. We selected stays during which a VTE occurred but was not the main reason of hospitalization (cancer was classified as primary/related diagnosis and VTE as significant associated diagnosis). Those stays were matched and compared to similar stays (same cancer and same reason for hospitalization) without VTE. Costs were calculated using the French official tariffs, from the perspective of the third-party payer. Results: We identified 214 stays for breast cancer during which a VTE occurred and was classified as significant associated diagnosis, 843 stays for colon cancer, 1301 for lung cancer, and 126 for prostate cancer. The comparison between those stays and similar stays without VTE showed significant increase of hospital stay duration in patients experiencing VTE. Median duration rose from 4 to 7 days in BC patients, from 8 to 16 days in CC, from 2 to 9 days in LC and from 6 to 10 days in PC. Consequently, the median expenditure per stay increased by 37% in BC patients with VTE (up to € 5,518), by 61% in CC (up to € 9,878), by 202% in LC (up to € 7,308) and by 22% in PC (up to € 6,200). Conclusions: When occurring during hospitalization, VTE made cancer management much heavier: patients faced prolonged hospital stays whereas healthcare system faced significant additional cost. Better prevention and follow-up measures could reduce this burden, and benefit both patients and hospitals.