Background: Sarcopenia is prevalent in older populations with many causes and varying outcomes however information for use in clinical practice is still lacking. Aims: The aim of this report is to identify the clinical determinants and prognostic significance of sarcopenia in a cohort of hospitalized acutely ill older patients. Methods: Four hundred and thirty two randomly selected patients had their baseline clinical characteristic data assessed within 72 h of admission, at 6 weeks and at 6 months. Nutritional status was assessed from anthropometric and biochemical data. Sarcopenia was diagnosed from low muscle mass and low muscle strength-hand grip using anthropometric measures based on the European Working Group criteria. Results: Compared with patients without sarcopenia, those diagnosed with sarcopenia 44 (10%) were more likely to be older, have more depression symptoms and lower serum albumin concentration. The length of hospital stay (LOS) was significantly longer in patients diagnosed with sarcopenia compared with patients without sarcopenia [mean (SD) LOS 13.4 (8.8) versus 9.4 (7) days respectively, p = 0.003]. The risk of non-elective readmission in the 6 months follow up period was significantly lower in patients without sarcopenia compared with those diagnosed with sarcopenia (adjusted hazard ratio .53 (95% CI: .32 to .87, p = 0.013). The death rate was also lower in patients without sarcopenia 38/388 (10%), compared with those with sarcopenia 12/44 (27%), p-value = .001. Conclusion: Older people with sarcopenia have poor clinical outcome following acute illness compared with those without sarcopenia.