Objective This study aimed to determine whether preresection serum CRP level independently predicts survival among patients with resectable non–small cell lung cancer. Methods Clinical, pathologic, and laboratory data from 300 patients operated on for non–small cell lung cancer in a single institution were studied in univariate and multivariate survival analyses. Validation was sought in another cohort of 68 similar patients from another institution. Results In the main cohort, preoperative CRP value was 3 mg/L or lower in 136 patients (45.3%), between 4 and 20 mg/L in 89 (29.7%), and greater than 20 in 64 (21.3%). CRP level was significantly associated with chronic bronchitis, hypoalbuminemia, pathologic stage, and peritumoral vascular emboli. Overall, 5-year survivals of patients with preoperative CRP 3 mg/L or lower, between 4 and 20 mg/L, and greater than 20 mg/L were 55.6%, 45.6%, and 40.0%, respectively ( P = .0571). In multivariate analysis, CRP level greater than 20 was significantly associated with survival, but with significant interaction between CRP level and disease stage ( P = .02). Patients in stage I or II disease with CRP levels greater than 20 had worse survival than did patients with undetectable CRP (adjusted hazard ratio, 1.874; 95% confidence interval, 1.039–3.381); the difference was not significant in stages III and IV. In the validation series, CRP level greater than 20 mg/L also predicted worse survival ( P = .018). Conclusions Preoperative CRP level greater than 20 mg/L is significantly associated with worse survival than undetectable CRP in patients with stage I or II non–small cell lung cancer.