Purpose To review trends in the use of postoperative radiotherapy (PORT) for stage II and III incompletely resected non–small-cell lung cancer (NSCLC) and evaluate the association between PORT and survival in such patients. Patients and Methods We identified patients with pathologic stage N0-2, overall American Joint Committee on Cancer stage II or III NSCLC within the National Cancer Data Base who had undergone a lobectomy or pneumonectomy with positive surgical margins. Only patients coded as receiving external-beam PORT at 50 to 74 Gy or observation were included. To account for perioperative mortality, we excluded patients who survived less than 4 months after diagnosis. Multivariable logistic regression was used to determine factors associated with PORT receipt. Cox proportional hazards regression was performed for multivariable analyses of overall survival. Results Among 3,395 included patients, 1,207 (35.6%) received PORT. Predictors for the use of PORT among this patient population included age less than 60 years, treatment in a nonacademic facility, earlier year of diagnosis, decreased travel distance, lower nodal stage, and chemotherapy receipt. On multivariable analysis adjusting for demographic and clinicopathologic covariates, PORT (hazard ratio, 0.80; 95% CI, 0.70 to 092) was associated with improved survival. Subset analysis by nodal stage showed that PORT improved survival across all nodal stages. Conclusion PORT is associated with improved overall survival in patients with incompletely resected stage II or III N0-2 NSCLC. The use of PORT for this population in more recent years has been declining. In the absence of randomized trials evaluating PORT utilization for this patient population, our findings strongly support the delivery of PORT in patients with incompletely resected NSCLC.