Background: Patients with lung cancer (LC) are at significantly higher risk of developing venous thromboembolism (VTE), which may lead to increased use of health resources and the cost of the disease management. The main aim of the study was to determine the cost of the management of VTE events in patients with LC treated with Low Molecular Weight Heparins (LMWH) in Spain. Methods: Costecat was an observational, ambispective pharmacoeconomic study. Patients with LC, with a first episode of VTE (symptomatic or incidental) in treatment with LMWH, were recruited from six third-level hospitals and followed up for six months. Sociodemographic, clinical and resource use variables of VTE-related implications and its treatment were collected. Direct healthcare costs and direct non-healthcare costs were recorded. Data collection was documented in an electronic case report. Costs (€2018) were estimated from the healthcare perspective. Statistical analysis was performed using the statistical program R 3.4.3 version (30 November 2017). Results: Forty-seven patients were included. Mean age was 65.4 years, 66.0% were male. The percentage of patients with LC who had metastatic disease was 78.7%. Twenty-three patients (48.9%) needed hospital admissions due to thromboembolic episode. Total average cost of patients with cancer associated VTE (CAT) was €10,969.6 per patient/semester. The hospitalizations represent 65.8% of total costs (7207.3 € SD 13,996.9 €), followed by LMWH therapy which represents 18.6% (2033.8 € SD:630.5 €). Conclusions: Venous thromboembolism episodes induce an economic impact on patients and healthcare systems. Direct healthcare costs are the major burden of the total cost, in which hospitalizations are the main drivers of cost.