Recent studies have indicated that the C-reactive protein (CRP)/albumin (CRP/Alb) ratio is associated with clinical outcomes in patients with various carcinomas. However, no studies have explored the association between the ratio of CRP/Alb and clinical outcome of inoperable patients with nonsmall cell lung cancers (NSCLCs). We examined the prognostic impact of CRP/Alb ratio on 165 stage IV NSCLC receiving palliative chemotherapy. The optimal cutoff level of CRP/Alb ratio was set at 0.195. The median follow-up time was 9 months (range, 1–74 months). On univariate analysis, high CRP/Alb ratio (≥0.195) was correlated (P < .001) with poorer overall survival (OS). Subgroup analysis of adenocarcinoma showed that CRP/Alb ratio was significantly (P < .001) associated with OS. Multivariate analysis showed that CRP/Alb ratio was an independent prognostic factor for OS (hazard ratio: 2.227, P = .001). Subgroup analysis revealed that the CRP/Alb ratio had a significant (P = .001) prognostic impact on adenocarcinoma patients receiving platinum chemotherapy. Elevated CRP/Alb ratio was significantly associated with male gender (P = .002) and smoking history (P = .009). The results of this study suggest that the CRP/Alb ratio might be used as a simple, inexpensive, and independent prognostic factor for OS of patients with advanced lung adenocarcinomas receiving platinum chemotherapy.