Background Comprehensive analysis of prognostic significance of marital status in patients with stage III non-small-cell lung cancer (NSCLC) when adjusted for patient-, disease-, and treatment-specific factors, including the interaction with racial, nutritional, and immunologic status, is lacking. Objective To evaluate whether marital status is an independent predictor of clinical outcomes in patients with stage III NSCLC who are treated uniformly with curative intent. Methods The Kaplan-Meier method and Cox proportional hazards model were used to estimate the overall survival and freedom from recurrence (FFR) in 355 patients with stage III NSCLC who were treated during 2000-2013. Results 52% of patients in the cohort were married and were more likely to self-identify as white (P < .0001), reside in zip codes with a higher household median income (P < .0001), have Eastern Cooperative Oncology Group Performance Status of 0 (P = .001), have higher pretreatment albumin (P = .009), undergo surgery (P = .001), and have insurance (P = .029). On multivariate analysis, marital status remained an independent predictor of survival and was associated with a 40% decreased risk of death (P < .0001), further stratifying outcomes beyond gender and stage grouping. FFR was comparable between the 2 groups (P = .108). Limitations Retrospective analysis; information on individual support system beyond the marital and insurance status and zip code income was not available. Conclusions In a cancer such as NSCLC, in which modern therapeutic approaches have yielded only modest survival improvements despite considerable treatment-related toxicity, marital status remains an independent predictor for survival. Marriage is likely a surrogate for better psychosocial support; the scale of survival improvements seen justifies investments into supportive care interventional strategies to help advance overall outcomes.