Differentiating sepsis from other noninfectious causes of systemic inflammation is often difficult in the elderly. The aim of this study was to evaluate the ability of C-reactive protein (CRP), Erythrocyte Sedimentation Rate (ESR), procalcitonin (PCT), and Interleukin-6 (IL-6) to identify elderly patients with sepsis. In this single center prospective observational study, we included all consecutive elderly patients admitted with suspected sepsis and systemic inflammatory response syndrome (SIRS) in an emergency department. Blood samples for measuring CRP, PCT, IL-6, ESR and white blood cells (WBC) count were taken at first day of admission. Sensitivity, specificity, positive and negative predictive values were calculated for each inflammatory markers being studied. A total of 150 elderly patients aged 65 and older, 50 with sepsis and 50 with SIRS, and fifty individuals in a normal health status were included. CRP exhibited the greatest sensitivity (98%) and negative predictive value (98.6%) and performed best in differentiating patients with sepsis from those with SIRS. In a receiver operating characteristic curve analysis, IL-6 performed best in distinguishing between SIRS and the control group (AUC 0.75, 95% CI). On the other hand, both CRP and ESR appeared to be a more accurate diagnostic parameter for differentiating sepsis from SIRS among elderly patients.