Background: Lobectomy is the current standard of care for patients with stage I non-small cell lung cancer (NSCLC). There is a lack of prospective data on the benefit of adjuvant chemotherapy (CT) in patients with negative margins but with high-risk features: lympho-vascular invasion (LVI) or visceral pleural invasion (VPI). We aimed to investigate the benefit of adjuvant CT in patients with pathological stage I NSCLC with high-risk features. Methods: The 2016 National Cancer Database was queried to identify patients with pathological stage I NSCLC (8^th edition AJCC staging) diagnosed from 2010-2015 who received lobectomy/pneumonectomy with clear surgical margins. Patients were stratified into high risk (tumor size ≥2 cm with LVI and/or VPI) or low risk group. Multivariate Cox proportional hazards regression and propensity score matched Kaplan-Meier survival analysis were used to compare overall survival between those who received adjuvant CT and those who did not. Results: 34,556 patients were identified with 1114 (3.2%) receiving adjuvant CT. On multivariate Cox regression analysis, high risk tumors (hazard ratio [95% confidence interval] = 1.31 [1.25-1.38]) and lack of adjuvant chemotherapy (1.25 [1.09-1.44]) were associated with worse overall survival (OS). Additionally, male sex, age ≥ 60 years, higher comorbidity burden, lack of insurance, low facility volume, low median income, non-squamous histology were associated with worse OS. After propensity score matching, Kaplan-Meier survival analysis of the high risk subgroup (n = 2923) showed a significant difference in overall survival (OS) between those who received adjuvant CT (n = 1032, 5 year OS, 74.7%; 95% CI, 70.9%-78.0%) and those who did not (n = 1891, 5 year OS, 66.9%; CI, 63.9%-69.6%; p = 0.0002). In patients with no high risk factors for recurrence (n = 384), OS was not significantly different between the patients who received adjuvant CT (n = 78, 5 year OS, 75.8%; CI, 61.3%-85.5%) and those who did not receive adjuvant CT (n = 306, 5 year OS, 77.1%; CI, 70.0%-82.7%; p = 0.3). Conclusions: Our study showed better survival with adjuvant CT in patients with pathological stage I NSCLC who have tumor size greater than 2 cm, LVI and/or VPI.