Background: Elderly patients are a significant and increasing proportion of ICU patients. With advancing age, the comorbidities critically ill elderly patients have substantial mortality. The early recognition of patients at high risk of mortality is needed to plan care in advance and to control healthcare costs. Aim: To find out the admission clinical and laboratory predictors of mortality in critically ill elderly admitted to ICU. Method: A prospective study was performed in Geriatric ICU in Ain Shams University Hospitals including 90 critically ill elderly patients admitted for 24 hours or more. Each patient was subjected to on admission clinical assessment, in addition to laboratory investigations including; measurement of serum levels of Blood urea Nitrogen, Creatinine, Sodium, Potassium, Calcium, Phosphorus, Magnesium, Zinc, Bilirubin, Complete blood count (CBC), CRP and arterial blood gases. Results: Mortality accounted for 39% of patient‘s outcome. Advanced age was significantly associated with increased mortality (p=0.03) The acute stroke as a cause of admission was found to be associated with increased mortality (P= 0.00). Length of ICU stay and the use of mechanical ventilation significantly increased mortality (P= 0.01, P = 0.000) respectively. Tachycardia, tachypnea and deep coma were also found to be associated with increased mortality (P= 0.003, 0.02, 0.000) respectively. Hematocrit, bicarbonate, and sodium levels were significantly lower among the non survivors. Conclusions: The most important factors independently associated with the high risk of mortality among elderly admitted in ICU are; advanced age, impaired level of consciousness, need for mechanical ventilation, low serum sodium and bicarbonate levels. Early management of hyponatremia and metabolic acidosis is substantial for improving outcome in geriatric ICU.