Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is the most common type of autoimmune encephalitis. Here, we investigated the factors associated with poor prognosis and relapse in patients with anti-NMDAR encephalitis.In this single-center observational cohort study, we retrospectively analyzed 51 patients with anti-NMDAR encephalitis treated in our hospital from January 2014 to October 2022. The demographic data, clinical characteristics, scale scores, results of auxiliary examination, and treatment details were statistically analyzed. Based on modified Rankin Scale (mRS) scores measured before final discharge, patients were divided into groups with good (mRS score 0-2) and poor (mRS score 3-6) prognoses for functional evaluation. The chi-squared test or Fisher's exact test was used to compare categorical data, and the t-test and Mann-Whitney U test were used to compare normally and non-normally distributed continuous data, respectively. Binary logistic regression was used to identify the risk factors for prognosis and relapse.At admission, the main clinical manifestations observed were psychobehavioral disorders (50 cases, 98.0%), consciousness disorders (28 cases, 54.9%), epilepsy (33 cases, 64.7%), motor disorders (28 cases, 54.9%), speech disorders (24 cases, 47.1%), and dysfunction of the autonomic nervous system (15 cases, 29.4%). All 51 patients (100%) had mRS scores of 3-5 at admission, and 50 were treated with intravenous methylprednisolone and human immunoglobulin. A total of 22 patients (43.1%) had an mRS score of 3-6 at discharge, which was significantly lower than those at admission. One patient died (mRS score 6) after developing septic shock (fatality rate 1.9%). Binary logistic regression analysis showed that movement disorders/involuntary movement (odds ratios [OR] 3.778, p = 0.029), abnormal brain magnetic resonance imaging (OR 4.817, p = 0.013), electroencephalogram slow wave activity of >50% (OR 8.400, p = 0.001), a white blood cell count of >10 × 106/L in the cerebrospinal fluid (OR 3,210, p = 0.048), and male sex (OR 3.282, p = 0.050) were risk factors for poor prognosis. A duration of disease of >12 months (OR 8.800, p = 0.001) and first-line-immunotherapy for less than 3 months after first onset (OR 3.719, p = 0.048) were identified as risk factors for relapse.Motor disorders or involuntary movement, abnormal brain magnetic resonance imaging, electroencephalogram slow wave activity >50%, and elevated white blood cell counts in cerebrospinal fluid were associated with poor prognosis in patients with NMDAR encephalitis. First-line immunotherapy less than 3 months after first onset may be a risk factor for relapse.Copyright © 2023 Elsevier B.V. All rights reserved.