Identifying and managing critically unwell older patients in emergency departments are challenging for all clinicians. Physiologic changes, multiple comorbidities, and medications often mask or confound serious conditions in older people, and vital signs can be misleading. Because standard triage methods may be inadequate for this population, enhanced triage systems that incorporate frailty assessments and tailored scoring systems are useful. Serial assessments tailored to the patient, biomarkers, and advanced imaging are also important to better detect and manage critical illness in older adults and improve outcomes. Here, the authors discuss diagnosis and management of critically ill older adults.