BACKGROUND: The reported incidence of venous thromboembolism (VTE) in cancer patients is 4-20%. The Khorana VTE risk score (KRS) and the Vienna VTE risk score (VRS) have been proposed as scoring models for evaluation of cancer-associated VTE. However, the risk factors of VTE in Japanese lung cancer patients have not been clarified. METHODS: This retrospective study included 682 hospitalized Japanese patients with newly diagnosed lung cancer who were examined for VTE on admission between January 2014 and December 2016. RESULTS: Seventy-one (10.4%) of the 682 patients were diagnosed with VTE. Multivariate logistic regression analysis showed that body mass index (BMI) ≥25 kg/m2 (OR, 2.02; 95% CI, 1.06-3.72), white blood cell (WBC) count >11 × 109/L (OR, 2.31; 95% CI, 1.11-4.61), pre-chemotherapy serum D-dimer concentration ≥1.44 μg/mL (OR, 2.73; 95% CI, 1.49-4.99), and non-small cell lung cancer (OR, 3.13; 95% CI, 1.32-9.23) were significantly associated with VTE in these patients. The cut-off values for BMI, WBC count, and D-dimer concentration determined using receiver operating characteristic curves were 25.4 kg/m2, 11.2 × 109/L, and 1.95 µg/mL, respectively. CONCLUSIONS: In this study, we were able to identify four independent risk factors for cancer-associated VTE in Japanese lung cancer patients for the first time. Moreover, we showed that a cut-off level of ≥25 kg/m2 for BMI was a risk factor for VTE in this cohort.