The objective of this study is to externally validate the recently published Revised International Prognostic Scoring System (IPSS-R) for myelodysplastic syndrome (MDS) and compare it with the International Prognostic Scoring System (IPSS). We conducted a retrospective study of 173 adult MDS patients who had not received disease-altering treatment. Using the Cox hazard method, we found the IPSS-R to be a significant predictor of survival (p < 0.001, hazard ratio, HR = 1.82, 95% confidence interval, CI 1.57-2.12) and time to acute myeloid leukemia (AML; p < 0.001, HR = 2.05, 95% CI 1.55-2.70). The IPSS-R has greater prognostic power for survival and time to AML compared with the IPSS, given higher Somers' D values (0.41 vs. 0.39 and 0.55 vs. 0.53, respectively). Using the log-rank test, we found a significant difference when comparing IPSS-R groups (p < 0.02), with the exception of the high-risk versus very high-risk group comparison. The IPSS-R reclassified low-risk and intermediate-1 IPSS groups into four groups (log-rank, p < 0.001) and intermediate-2 and high-risk IPSS groups into three groups (log-rank, p < 0.04, excluding high-risk vs. very high-risk comparison). We conclude that the IPSS-R has significant prognostic utility for MDS patients.