Purpose: As stereotactic body radiation therapy (SBRT) has emerged as a quick, effective, and well-tolerated treatment for early stage non-small cell lung carcinoma (NSCLC), it can be difficult to convince patients to quit smoking in follow-up. We evaluated whether there was a survival benefit to smoking cessation after SBRT. Methods and materials: Patients with early-stage NSCLC treated from 2004 to 2013 who were still smoking tobacco at the time of SBRT were identified from a prospective institutional review board-approved registry. Peripheral tumors were treated to 54 Gy in 3 fractions and central tumors to 50 Gy in 5 fractions. Patients were reviewed for overall survival (OS) and disease progression. The log-rank and Cox regression tests were used to identify factors predictive of OS. Results: Thirty-two patients (27%) quit smoking after SBRT, and 87 (73%) continued smoking. Median follow-up was 22 months (range, 2-87). On multivariate analysis, smoking status (hazard ratio, 2.1; 95% confidence interval, 1.02-4.2; P = .045), increasing age-adjusted Charlson comorbidity score and larger tumor size were predictive of worse OS. The prior number of cigarette pack-years was not significant (. P = .62). In a Kaplan-Meier comparison, smoking cessation after SBRT was associated with improved 2-year OS, 78% versus 69% (. P = .014). There was no significant difference in 2-year progression-free survival (75% vs 55%, P = .23) or local control (97% vs 88%, P = .63). Conclusion: OS is significantly improved in patients who stop smoking after SBRT for early-stage NSCLC, no matter their previous smoking history. Encouraging smoking cessation should be an important part of every posttreatment visit.