Purpose Radiotherapy (RT) is known to effectively palliate many symptoms of patients with metastatic non–small-cell lung cancer (NSCLC). Anecdotally, RT is believed to be commonly used in this setting, but limited population-based data are available. The objective of this study was to examine the utilization patterns of palliative RT among elderly patients with Stage IV NSCLC and, in particular, to identify factors associated with its use. Methods and Materials A retrospective population-based cohort study was performed using linked Surveillance, Epidemiology and End Results (SEER)-Medicare data to identify 11,084 Medicare beneficiaries aged ≥65 years who presented with Stage IV NSCLC in the 11 SEER regions between 1991 and 1996. The primary outcome was receipt of RT. Logistic regression analysis was used to identify factors associated with receipt of RT. Results A total of 58% of these patients received RT, with its use decreasing over time ( p = 0.01). Increasing age was negatively associated with receipt of treatment ( p <0.001), as was increasing comorbidities ( p <0.001). Factors positively associated with the receipt of RT included income ( p = 0.001), hospitalization ( p <0.001), and treatment with chemotherapy ( p <0.001). Although the use varied across the SEER regions ( p = 0.001), gender, race/ethnicity, and distance to the nearest RT facility were not associated with treatment. Conclusions Elderly patients with metastatic NSCLC frequently receive palliative RT, but its use varies, especially with age and receipt of chemotherapy. Additional research is needed to determine whether this variability reflects good quality care.