Purpose To assess the predictive value of three different frailty domains (physical, psychological, social) for both readmission and mortality in a population of acutely admitted older patients, and to determine which components of the individual three frailty domains had an effect on readmission and mortality. Methods This prospective cohort study was conducted in a sample of 1,328 Danish acutely admitted patients aged 65 years or older. The follow-up period on readmission and death was six months. The Tilburg Frailty Indicator (TFI), a validated questionnaire, was used to assess the three frailty domains and their 15 components. Results After using sequential logistic regression analyses, including controlling for socio-demographic characteristics and comorbidity, physical and social frailty predicted readmission and death, while psychological frailty predicted only readmission. The analyses also demonstrated that the component weight loss had predictive value for both outcomes, and feeling down and missing people around you were only associated with readmission, after controlling for all the predictors. Conclusion Our study emphasizes the importance of a multidimensional measurement of frailty, including a physical, psychological and social domain. Health care professionals aiming to prevent readmission and death among acutely admitted patients should at least conduct interventions focused on unintentional weight loss, feeling down, and missing people around you, because their effect on the outcomes was the largest.