Delirium is a frequent neurocognitive complication in patients with cancer, particularly in patients with advanced-stage disease (in whom a combination of factors might trigger an episode) and in patients with a high degree of predisposing vulnerability, such as the elderly or patients with dementia. The communicative impediments associated with delirium generate distress for the patient and their family, and substantive challenges for health-care practitioners, who might have to contend with agitation, and difficulty in assessing pain and other symptoms. Validated assessment tools exist for screening, diagnosing and monitoring the severity of delirium in cancer care. The level of investigative and therapeutic intervention in a delirium episode is determined by the patient's estimated prognosis and the agreed goals of care. Although delirium is ominously associated with the terminal phase of life, part or complete reversal can be possible depending on the nature of the precipitating factors, and on whether investigation and treatment of these factors is consistent with the established goals of care. Pharmacological treatment for symptom control is indicated for most patients with delirium, and antipsychotics are the drugs of choice, but some patients with refractory and nonreversible delirium can require continuous deep sedation with agents such as midazolam.