We sought insights into neuromyelitis optica spectrum disorder (NMOSD) treatment practices worldwide.Neurologists from the USA, Germany, Italy, Brazil, South Korea, and China completed an online survey, contributing clinical records for aquaporin-4 (AQP4) immunoglobulin G (IgG)-seropositive adults with NMOSD, which included patient demographics, diagnosis, maintenance treatment history, relapse occurrence, and severity. Interviewed patients receiving NMOSD maintenance therapy provided information about their diagnosis, treatment, perceptions about relapse severity or disease stability, and treatment switches.A total of 389 neurologists submitted clinical records for 1185 patients with AQP4-IgG-seropositive NMOSD; 33 patients with NMOSD were interviewed. Approximately 25% (228/910) of patients from the clinical record review (CRR) were initially misdiagnosed; 24% (8/33) of patients interviewed reported formal misdiagnosis. Misdiagnosis was associated with treatment delay and more relapses compared with correct diagnosis (mean 3.3 vs 2.8). Maintenance therapy was not initiated within 2 months for 47% (221/472) of patients from the CRR and 24% (8/33) of interviewed patients. Oral corticosteroids/immunosuppressive therapies were typically the first maintenance treatment initiated, except for the USA, where monoclonal antibodies were equally likely to be prescribed. Relapse severity influenced the decision to initiate/change therapy and use monoclonal antibodies. Of interviewed patients, 76% (25/33) did not recall having a choice of treatment and many did not know the rationale for treatment choice.Misdiagnosis of NMOSD appears to be common and is associated with a delay in initiation of maintenance therapy, with decisions influenced by relapse severity. Further real-world studies assessing relapse severity in treatment initiation/switch are required to revise NMOSD treatment recommendations.© 2023. The Author(s).