The performance of a prognostic score must be evaluated prior to being used. The aim of the present study was to evaluate the predictive ability of hospital mortality of Simplified Acute Physiology Score 3 (SAPS 3) score in elderly patients admitted to Intensive Care Units (ICUs). The aim of the present study was to evaluate the SAPS 3 score predictive ability of hospital mortality in elderly patients admitted to ICU. This study was conducted as a prospective cohort, in two mixed ICUs. Two hundred and eleven elderly patients were included. None. We compared the predictive accuracy of SAPS 3 measured at the first hour at ICU and Acute Physiology and Chronic Health Evaluation II (APACHE II) measured with the worst values in the first 24 h at ICU. The patients were followed until hospital discharge. Evaluation of discrimination through area under curve receiver operating characteristic (aROC) and calibration by Hosmer-Lemeshow (HL) test. The median age was 68 years. The hospital mortality rate was 35.54%. The mean value of SAPS 3 was 62.54 ± 12.51 and APACHE II was 17.46 ± 6.77. The mortality predicted by APACHE II was 24.98 ± 19.96 and for standard SAPS 3 equation 41.18 ± 22.34. The discrimination for SAPS 3 model was aROC = 0.68 (0.62-0.75) and to APACHE II aROC = 0.70 (0.63-0.78). Calibration: APACHE II with HL 10.127 P = 0.26, and standard SAPS 3 equation HL 7.204 P = 0.51. In this study, the prognostic model of SAPS 3 was not found to be accurate in predicting mortality in geriatric patients requiring ICU admission.