Background: Adjuvant chemotherapy (AC) have been shown to improve overall survival in non-small cell lung cancer (NSCLC). Despite showing significant survival benefit across various age groups, patients are known to refuse AC. However, the factors associated with such a decision remain poorly understood in lung cancer. We therefore sought to investigate the factors associated with AC refusal in a nationally representative database in the United States (US). Methods: From 2004 to 2017, adults (≥20 years) with histologically confirmed non-small cell lung cancer (NSCLC) who underwent complete resection and were deemed to be chemotherapy eligible (node-positive or size ≥5 cm) were identified in the National Cancer Database (NCDB). Annual trends and factors associated with refusal of AC in chemotherapy-eligible NSCLC patients were evaluated using Joinpoint regression and multivariable logistic regression. Results: Among the 44,957 patients who met the inclusion criteria, 18,468 (3,678 (8.2%)) were noted to refuse chemotherapy in the NCDB. Patients refusing adjuvant chemotherapy were more likely to be elderly (OR 1.08, 95% CI, 1.07-1.08; P<.001), uninsured when compared with government insurance (OR 1.79, 95% CI, 1.38-2.33; P<.001), treated in the Western region of the when compared with patients in the Northeast (OR 1.47, 95% CI, 1.28-1.68; P<.001). They were also more likely to have a higher Charlson score versus patients with Charlson score of zero (OR 1.31, 95% CI, 1.18-1.46; P<.001), have squamous cell carcinoma versus adenocarcinoma (OR 1.20, 95% CI, 1.11-1.31; P<.001), undergo pneumonectomy versus lobectomy (OR 1.31, 95% CI, 1.16-1.47, P<.001), and have ≥2 weeks hospital length of stay versus < 2 weeks (OR 2.25, 95% CI, 1.93-2.63; P<.001). Conclusions: In our analysis, we identified several sociodemographic and clinicopathologic variables that were independently associated with chemotherapy refusal. We saw the number of patients refusing AC increased sharply during the study period. Our study shows that in addition to poor post-operative recovery, underlying sociodemographic factors might predict patients at risk for refusing adjuvant chemotherapy in lung cancer. Further understanding of these factors might help devise effective interventions to motivate patients to undergo potentially life-extending chemotherapy in lung cancer.