Background: Surgery or radiation therapy (RT) remains the definitive treatment for early-stage (Stage I/II) non-small cell lung cancer (NSCLC). Early-stage NSCLC should be treated appropriately since survival decreases progressively with advanced stages. Our study aims to identify the factors associated with receiving no definitive therapy among US patients. Methods: Patients ≥ 18 years and diagnosed with stage I/II NSCLC from 2004-2011 in Surveillance, Epidemiology and End Results Program (SEER) were identified. Definitive therapy was defined as receiving surgery and/or RT. Socio-economic characteristics (income, educational status and residence type) were collected at county-level. Predictors for no definitive therapy were estimated with a multivariable logistic regression model. Results: A total of 32,401 patients were identified. 4,997 patients (15%) had no definitive therapy and among them only 456 (9%) did not receive surgery due to contraindications/patient refusal. Independent predictors for no definitive therapy include individual characteristics, such as older age, male, African Americans, not-married status, histology types other than adenocarcinoma, as well as county-level characteristics include living in a county with lower median household income, higher percentage of population with education level < high school, and a non-metropolitan setting. Conclusions: A significant proportion of patients diagnosed with early-stage NSCLC in the US did not receive definitive therapy. Socio-economic characteristics should be explored further to explain this phenomenon.