Delirium is most common neuropsychiatric disorder that affects patients in surgical and internal medicine clinics. It is defined as a transient, usually reversible organic mental disorder that has a rapid onset and fluctuating course. Clinically, delirium is an acute or subacute organic mental syndrome that is characterized by a disturbance in attention (reduced ability to direct, focus, sustain, and shift attention), awareness (reduced orientation to the environment), and other cognitive abilities (e.g., memory deficit and disorientation) and is not better explained by preexisting, established, or other evolving neurocognitive disorders. Studies have found that between 10% and 20% of all adult inpatients are diagnosed with delirium and that it occurs in up to 50% of elderly inpatients. Delirium itself is not a disease but rather a clinical syndrome, which results from an underlying disease. There is evidence from the history, physical examination, or laboratory findings that the disturbance is a physiological consequence of an underlying medical condition, substance intoxication or withdrawal, use of a medication, or a toxin exposure, or it is a combination of these factors. Accurate identification of underlying causes and risk factors is essential in early stage diagnosis and treatment. Treatment of delirium requires the treatment of the underlying causes. Psychotropic medications are used to comfort patients or enable better patient management. This study aims to review the clinical characteristics, etiological and risk factors, and different methods to obtain an accurate diagnosis and treatment of delirium.