BACKGROUND: Cognitive impairment is a recognized long-term complication of anti-NMDAR encephalitis, but its pooled magnitude, domain specificity, and time course have not been systematically quantified. OBJECTIVE: To quantify pooled global cognitive and verbal episodic memory impairment in convalescent anti-NMDAR encephalitis relative to healthy comparators, and to assess whether impairment magnitude changes with time since disease onset. METHODS: We systematically reviewed observational studies assessing standardized cognitive outcomes in adults with cell-based-assay-confirmed anti-NMDAR encephalitis during the post-acute/convalescent phase. PubMed, Embase, Scopus, and CENTRAL were searched from inception to 20 June 2026. Random-effects meta-analyses were performed for cognitive domains with at least three independent cohorts, while other domains were synthesized narratively according to SWiM principles. RESULTS: Fourteen independent cohorts comprising 439 patients were included. Six cohorts (191 patients, 182 controls) contributed to the confirmed primary global-cognition analysis, showing substantial impairment (Hedges' g - 1.26, 95% CI - 1.49 to - 1.04; I²=0%). Verbal episodic memory was also impaired (g - 0.88, 95% CI - 1.13 to - 0.63; 5 cohorts). Recognition was impaired alongside recall in the two cohorts reporting recognition trials. Narrative synthesis identified frequent executive and working-memory impairment, impaired speeded processing, and deficits in visual episodic memory and language, whereas visuospatial findings were less consistent. CONCLUSIONS: Post-acute anti-NMDAR encephalitis is associated with substantial global cognitive and verbal episodic memory impairment, with additional deficits across several cognitive domains. Comprehensive longitudinal neuropsychological assessment, including social cognition and psychiatric symptoms, is needed to clarify recovery trajectories and mechanisms.