Background Inflammation-based prognostic scores such as the neutrophil lymphocyte ratio (NLR), platelet lymphocyte ratio (PLR), Glasgow prognostic score (GPS), and modified GPS (mGPS) have been reported to have prognostic value in patients with many types of cancer, including esophageal squamous cell carcinoma (ESCC). However, the role of the C-reactive protein/Albumin (CRP/Alb) ratio in ESCC has not yet been evaluated. Methods A total of 468 patients suffering from histologically proven ESCC were enrolled between January 2000 and July 2010. The GPS, mGPS, NLR, PLR and CRP/Alb ratios were tested together with established prognostic factors in univariate and multivariate Cox regression analyses of overall survival (OS). Results The optimal cutoff level for the CRP/Alb ratio was 0.50. The CRP/Alb ratio (continuous) had higher AUC values at 12 months (0.796), 24 months (0.805), and 36 months (0.815) than the NLR, GPS and mGPS. In univariate analysis, the 5-year OS rate for patients with a CRP/Alb ratio > 0.50 was 43.4%, while the rate for patients with a CRP/Alb ratio ≤ 0.50 was 17.7% (P 0.50 had worse survival than patients with a CRP/Alb ratio ≤ 0.50 (HR: 2.44; 95% CI: 1.82–3.26; P < 0.0001). Conclusion In summary, to the best of our knowledge, this is the first study to identify the CRP/Alb ratio as a novel inflammation-based prognostic factor in a large group of ESCC patients. The prognostic value of the CRP/Alb ratio needs to be verified in prospective multicenter studies.