Neuromyelitis optica (NMO) has a complex pathology. Clinical symptoms, derived from damage to optic nerves and spinal cord, cause optic neuritis and/or longitudinally extensive myelitis. Treatment options are limited. We assessed adrenocorticotropic hormone (ACTH) use in patients developing exacerbations on systemic steroid treatment and declining other treatments.Patients with NMO who initiated intravenous methylprednisolone (IVMP) for exacerbations and experienced a subsequent exacerbation on monthly IVMP or had inadequate response to IVMP received ACTH 80 U/d intramuscularly for 7 days (for acute relapse), followed by 80 U every 2 weeks (for long taper down/maintenance). Every 1 to 3 months, relapse, Expanded Disability Status Scale, laboratory, and adverse event assessments were performed.Six patients (mean age: 48.6 years; NMO-suggestive clinical/imaging presentations; cerebral spinal fluid revealing no oligoclonal bands; aquaporin-4 positive [n = 5]) were identified: 5 experiencing subsequent exacerbations with monthly IVMP and 1 with inadequate response to IVMP. No relapses occurred during ACTH treatment or taper-down period, laboratory values indicated no safety concerns, and annual follow-up magnetic resonance imagings were stable. Adverse events were generally characterized as improved or unchanged versus with IVMP, although 1 patient reported transient edema (lower extremities) only during ACTH treatment. Potential treatment-related AEs included edema, acne, urinary tract infection, and insomnia and were reportedly less severe with ACTH treatment than IVMP.Adrenocorticotropic hormone treatment for acute NMO was associated with clinical improvement, suggesting that ACTH could have a role in treating acute NMO patients failing IVMP and declining other treatments. Fewer/less severe AEs were observed with ACTH versus IVMP. Larger, controlled clinical studies are needed.