Background: There is growing evidence that misdiagnosis contributes to the high mortality rate in lung cancer patients complicated with pulmonary embolism (PE). This current study analyzed predictors of PE in lung cancer patients with lower extremity deep venous thrombosis (DVT) with the aim of personalizing the treatment and management of patients with PE. Methods: This retrospective case-control study included lung cancer patients with DVT at the emergency department of Shanghai Chest Hospital from January 2018 to December 2019. Patients were classified as having DVT with or without PE. The following characteristics were examined, including age, gender, smoking, hypertension, surgical trauma, hyperlipidemia, long-term bedridden status, calf swelling, coronary heart disease, chronic pulmonary disease, DVT location, DVT type, prothrombin time (PT), international normalized ratio (INR), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen, and D-dimer, and univariate and multivariate analyses were performed. Results: A total of 90 patients with lung cancer and DVT were analyzed, of whom 60% (54/90) had PE. Those variables independently associated to PE were hypertension [odds ratio (OR): 7.883, 95% confidence interval (CI): 2.038–30.495, P=0.003], long-term bedridden status (OR: 4.166, 95% CI: 1.236–14.044, P=0.021), and D-dimer levels (OR: 2.123, 95% CI: 1.476–3.053, P=0.000) were identified as independent risk factors for PE. The cut-off value of the receiver operating characteristic (ROC) curve for predicting PE by presented scoring system according to the risk factors was 1.5 and the area under the curve (AUC) was 0.84 (P<0.001). Conclusions: Hypertension, being bedridden for an extended period, and elevated serum D-dimer levels were independent risk factors of PE in lung cancer patients with lower extremity DVT. Novel strategies for patient management should be developed to decrease the risk of PE.