Background: The presence of cachexia at the time of cancer diagnosis and its influence on disease management and treatment outcomes for patients receiving radiotherapy are poorly described. Here, we assess the role of baseline cachexia in patients with NSCLC on first-line treatment modality and clinical outcomes. Methods: Retrospective review of medical records identified 1,334 patients with NSCLC consecutively treated at a tertiary care health system between 1/1/06 and 12/31/13. Cachexia was defined using the well-accepted and validated international consensus definition. The delivery of radiotherapy and its treatment intent were abstracted. Results: The cohort included a representative group of patients with a median age at diagnosis of 64 years, 47% females, and 32% patients of non-White race. Stage at diagnosis was I, II, III, and IV in 291, 105, 356, and 578 (43.3%) patients, respectively. Cachexia was present at the time of diagnosis in 403 (30.2%) patients including 18%, 14%, 32%, and 39% of stage I, II, III, and IV patients, respectively. Palliative intent radiotherapy was received by significantly more stage IV patients with cachexia (74%) than without cachexia (63%) (X², P = .01). In contrast, baseline cachexia was not associated with curative intent radiotherapy in stage I-III disease. At a median follow-up of 24 months, 857 deaths have been observed. Cachexia at the time of diagnosis was prognostic for worse survival by stage. For patients with stage IV NSCLC, median survival was 11 months for patients without cachexia but 6 months for patients with cachexia at diagnosis (P< .001). Cachexia remained significant in stage I NSCLC, with median survival of 45 and 67 months with or without cachexia at diagnosis, respectively (P = .03). Conclusions: Cancer cachexia at the time of diagnosis is common in patients with NSCLC even with early stage disease. The presence of cachexia at diagnosis is associated with utilization of radiotherapy as a palliative treatment. However, cachexia at diagnosis of NSCLC, even with early stage disease, is prognostic of worse outcomes despite curative intent radiotherapy.