Introduction: Stroke is common cerebrovascular disease in the elderly, which is characterized by neurological defects caused by cerebral vessels. Multiple studies have shown that miRNAs play important roles in stroke. In addition, a large number of evidence suggest that stroke increases the risk and severity of cognitive impairments. Methods: miR-511-3p expression levels were detected by real-time PCR. Receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic value of miR-511-3p in distinguishing stroke patients from healthy controls and to assess risk of post-stroke cognitive impairment (PSCI) in stroke patients. Pearson correlation coefficient was used to determine the relationship between miR-511-3p expression level and Montreal Cognitive Assessment Scale (MoCA) scores. Results: Serum miR-511-3p expression levels were decreased in stroke patients, and the decrease was more significant in PSCI patients. ROC curve results showed that miR-511-3p had high diagnostic accuracy in distinguishing healthy controls from stroke patients. Moreover, the expression level of miR-511-3p can be used as an independent predictor for the occurrence of PSCI and is positively correlated with MoCA scores of PSCI patients. Conclusion: miR-511-3p may be involved in the occurrence and development of stroke. In addition, miR-511-3p may be a novel biomarker for predicting PSCI occurred in stroke patients. These results may help improve the quality of prognosis of stroke.