Patients in acute settings may present with a variety of signs and symptoms; however, the principles of assessment are applicable to all acutely unwell patients. This article details a case study of a patient who presented to the author’s medical ward in a catatonic state, and was assessed using the ABCDE (airway, breathing, circulation, disability, exposure) approach. Catatonia is a disturbed mental state in which a patient exhibits abnormal behaviour, such as the inability to speak and non-responsiveness to stimuli, alongside immobility. Although catatonia is a rare condition, it is important that nurses can identify its signs and symptoms, because it can be fatal if not treated appropriately and rapidly. Thus, it is crucial for nurses to be able to systematically assess acutely unwell patients, including those with catatonia, using the ABCDE approach.