To explore the correlation between the geriatric nutritional risk index (GNRI) and post-stroke cognitive impairment (PSCI) in patients with acute ischemic stroke. Methods: Three hundred and sixty-eight patients with acute ischemic stroke were enrolled. Clinical baseline data were collected to calculate the admission GNRI level and assess the nutritional status. Based on their GNRI scores, patients were categorized into two groups: GNRI reduced group (with nutritional risk, GNRI<98) and GNRI normal group (without nutritional risk, GNRI≥98). Cognitive function was assessed by the mini-mental state examination (MMSE) scale at 3 months after stroke onset, and patients were categorized into PSCI and non-PSCI groups according to their scores. The correlation between GNRI index and MMSE scale scores was analyzed using Pearson's test. Additionally, factors influencing PSCI were explored by multifactorial Logistic regression analysis. Results: The incidence of PSCI was 21.9%. There were significant differences in gender, age, years of education, hypertension, baseline NIHSS scores, TOAST typing, GNRI reduction rate and GNRI scores between the PSCI and non-PSCI groups (P<0.05). Orientation, verbal ability and MMSE total score between patients in the GNRI reduction group and the GNRI normal group had a statistically significant difference (P<0.05). Pearson correlation analysis showed a positive correlation between GNRI and MMSE total score (r=0.654, P= 0.034). Multivariate Logistic regression analysis showed that reduced GNRI was significantly associated with the occurrence of PSCI in patients with ischemic stroke (OR=2.63, 95% CI 1.41～4.90). After adjusting for age, years of education, male sex, and hypertension, reduced GNRI remained significantly associated with the occurrence of PSCI (OR=2.45, 95% CI 1.27～4.56). Conclusion: There is a positive correlation between GNRI and MMSE scores in patients with acute ischemic stroke, and a decrease in GNRI is an independent risk factor for the occurrence of PSCI.