Background: Delirium, a common complication of advanced cancer, may put caregivers at risk for poor mental health outcomes. We looked for a relationship between caregiver-perceived delirium in a patient with advanced cancer and rates of caregiver psychiatric disorders.Methods: Using cross-sectional data from 200 caregivers of patients with cancer with a life expectancy of less than 6 months, we determined the frequency of caregiver-perceived delirium, which was defined as caregivers who reported witnessing the patient "confused, delirious" on the Stressful Caregiving Response to Experiences of Dying (SCARED) weekly or more often. We tested for associations between caregiver-reported delirium and presence of caregiver mental disorders, using the Structured Clinical Interview for the DSM-IV to diagnose mental disorders and caregiver burden, as measured by the caregiver burden scale (CBS).Results: Of the 200 caregivers who completed the SCARED, 38 (19.0%) reported seeing the patient "confused, delirious" at least once per week in the month prior to study enrollment and 7 (3.5%) met criteria for generalized anxiety (GA). Caregivers of patients with caregiver-perceived delirium were 12 times more likely to have GA (odds ratio [OR] ؍ 12.12; p Ͻ 0.01). The relationship between caregiver-perceived delirium and caregiver GA persisted after adjusting for caregiver burden and exposure to other stressful patient experiences (OR ؍ 9.99; p ؍ 0.04).Conclusions: This is the first report of an association between caregiver-perceived delirium and a caregiver mental health outcome. Further studies, using improved measures of delirium, are needed.