Purpose Many investigations on prognostic factors in lung cancer have been conducted; however, little is known regarding the outcomes of lung cancer cases complicated by deep vein thrombosis (DVT). This study aimed to determine the risk factors and impact on outcomes of lung cancer patients concurrent with DVT. Methods Lung cancer patients who underwent lower-extremity venous ultrasound were enrolled in this study. The patients were divided into a DVT group and a non-DVT group. Demographic information, clinical characteristics, and survival were analyzed by t-test, Wilcoxon test, chi-squared test, and logistic regression analysis. Results Of the 160 enrolled lung cancer patients, DVT was detected in 30 patients. Among the DVT group, adenocarcinoma was the most common histological type (27/30, 90.00%). Lung cancer complicated with DVT was associated with advanced stage, more severe myocardial injury, and a hypercoagulable state (P < .05). Differences in driver genes between the two groups were not significant. Radiologically, lung cancer patients with DVT were more likely to present with pericardial effusion and pleural effusion than patients without DVT (P < .05). Following multivariable logistic regression analysis, advanced stage (OR 5.368, [95%CI 1.871-18.165], P = .021), NT-proBNP >300 pg/ml (OR 5.575, [95%CI 1.733-3.722], P = .018), D-dimer >5 mg/L (OR 8.449, [95%CI 4.323-18.536], P = .004), CRP >12 mg/L (OR 6.687, [95%CI 1.967-13.617], P = .010), and serum CEA >25 ng/ml (OR 4.755, [95%CI 1.358-3.123], P = .029) were independent risk factors for adenocarcinoma complicated with DVT. Finally, survival analysis revealed that the occurrence of DVT resulted in a poorer prognosis despite anticoagulant therapy (P < .05). Conclusion DVT is a potential complication in patients with lung adenocarcinoma and could represent a prognostic marker for unfavorable outcome. It is essential to screen for DVT in high-risk adenocarcinoma patients.