Adults with Parkinson disease (PD) are hospitalized at higher rates than age-matched controls, and these hospitalizations are associated with significant morbidity. However, little is known about the consequences of critical illness requiring intensive care unit (ICU)-level care in patients with PD. The aim of this study was to define the characteristics and outcomes of adults with PD admitted to the ICU. We performed a retrospective nested case-control study using the Medical Information Mart for Intensive Care IV data set. Adults with PD were identified, and the index ICU admission for these subjects was matched 1:4 with index ICU admissions without a PD diagnosis based on age, sex, comorbidities, illness severity, ICU type, and need for mechanical ventilation. Primary outcomes were in-hospital mortality and discharge location. Secondary outcomes were length of stay and prespecified complications. A total of 630 adults with PD were identified. Patients with PD were older and were more likely to be male, have more comorbidities, and have higher illness severity at presentation. A matched analysis revealed adults with PD did not have a significant difference in in-hospital mortality but were more likely to be discharged to ahigher level of care. Adults with PD had longer hospital lengths of stay and increased odds of delirium, pressure ulcers, and ileus. During critical illness, patients with PD are at increased risk for longer hospital lengths of stay and complications and require a higher level of care at discharge than matched controls. These findings reveal targets for interventions to improve outcomes for patients with PD and may inform discussions about goals of care in this population.