Background: Oxaliplatin- and irinotecan-based combination chemotherapy with infusional 5-FU and leucovorin are currently the standard therapies for metastatic colorectal cancer. The objectives of this study were to evaluate the efficacy of capecitabine monotherapy as third line therapy for metastatic colorectal cancer after failure of chemotherapy containing oxaliplatin and irinotecan, and to determine whether the neutrophil-lymphocyte ratio (NLR), or the platelet-lymphocyte ratio (PLR) are significant prognostic marker in metastatic colorectal cancer. Methods: We analyzed 60 patients with metastatic colorectal cancer who received capecitabine monotherapy after the failure of FOLFOX and FOLFIRI. Capecitabine was administered at 1250 mg/m2 twice daily for 2 weeks, every 3 weeks. The NLR and PLR were calculated from complete blood counts in baseline laboratory test before the first cycle chemotherapy. Results: The overall response rate was 6.7% and stable disease was 41.7%. The disease control rate was 48.3%. The median progression-free survival (PFS) was 2.8 months (95% CI, 1.5-4.1 months) and the median overall survival (OS) was 9.7 months (95% CI, 7.6-11.7 months). The most frequent adverse event was hand-foot syndrome (all-grade 26.6%; grade3 5%). The response of capecitabine, NLR, and PLR were observed as good prognostic markers of OS in univariate analysis (p<0.001, 0.004, and 0.002, respectively). The response of capecitabine and PLR were independent prognostic marker in multivariate analysis (Hazard ratio 2.757, 95% CI 1.357-5.599, p=0.005 and hazard ratio 2.091, 95% CI 1.231-3.552, p=0.006, respectively). Conclusion: The capecitabine monotherapy showed a moderate disease control and a tolerable toxicity profile as third line treatment for metastatic colorectal cancer. The response of capecitabine and PLR may be simple and useful prognostic index for metastatic colorectal cancer.