This study examined real-world clinical outcomes such as progression-free survival (PFS), time to metastasis (TTM), overall survival (OS), and health-related quality of life (HRQOL) in patients with unresected stage III non-small cell lung cancer (NSCLC) treated in the community setting. A retrospective review of medical records extracted from 10 US community oncology practices was conducted. Most patients (58.2%) experienced disease progression, which the LMM showed to be associated with significant worsening of physical symptoms and psychological states (p < 0.001). This study documented PFS and OS consistent with published literature. The majority of patients experienced disease progression, which was associated with worsening of HRQOL. These findings highlighted the need for better therapeutic options in patients with unresected stage III NSCLC with potential to improve patient outcomes and HRQOL.