OBJECTIVES: To report the epidemiology, treatments, and outcomes of adult patients admitted to the ICU after cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome. DESIGN: Retrospective cohort study SETTING: Nine centers across the U.S. part of the chimeric antigen receptor-ICU initiative. PATIENTS: Adult patients treated with chimeric antigen receptor T-cell therapy who required ICU admission between November 2017 and May 2019. INTERVENTIONS: Demographics, toxicities, specific interventions, and outcomes were collected. RESULTS: One-hundred five patients treated with axicabtagene ciloleucel required ICU admission for cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome during the study period. At the time of ICU admission, the majority of patients had grade 3–4 toxicities (66.7%); 15.2% had grade 3–4 cytokine release syndrome and 64% grade 3–4 immune effector cell-associated neurotoxicity syndrome. During ICU stay, cytokine release syndrome was observed in 77.1% patients and immune effector cell-associated neurotoxicity syndrome in 84.8% of patients; 61.9% patients experienced both toxicities. Seventy-nine percent of patients developed greater than or equal to grade 3 toxicities during ICU stay, however, need for vasopressors (18.1%), mechanical ventilation (10.5%), and dialysis (2.9%) was uncommon. Immune Effector Cell-Associated Encephalopathy score less than 3 (69.7%), seizures (20.2%), status epilepticus (5.7%), motor deficits (12.4%), and cerebral edema (7.9%) were more prevalent. ICU mortality was 8.6%, with only three deaths related to cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome. Median overall survival time was 10.4 months (95% CI, 6.64–not available mo). Toxicity grade or organ support had no impact on overall survival; higher cumulative corticosteroid doses were associated to decreased overall and progression-free survival. CONCLUSIONS: This is the first study to describe a multicenter cohort of patients requiring ICU admission with cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome after chimeric antigen receptor T-cell therapy. Despite severe toxicities, organ support and in-hospital mortality were low in this patient population.