Delirium (or Acute Confusional State) refers to an acute alteration of attention, consciousness, and cognitive performance. Particularly the hypoactive subtype of delirium represents a diagnostic and clinical challenge. As symptoms of hypoactive delirium may overlap with the clinical picture present in dementia and depression, correct diagnostic differentiation can be challenging. In the absence of timely diagnosis and treatment, hypoactive delirium can last for several weeks. Apart from the health consequences for the patient, such a long course can stress caregivers and the family to their very limit. In this article, we will address the particularities of hypoactive delirium in hospital practice, the neurobiological bases of this disorder, the challenges it represents at the diagnostic level as well as its recommended management according to current literature.