Acute ischemic stroke (AIS) has a high risk of recurrence, particularly in the early stage. The purpose of this study was to assess the frequency and risk factors of in-hospital recurrence in patients with AIS in China. A retrospective analysis was performed of all of the patients with new-onset AIS who were hospitalized in the past three years. Recurrence was defined as a new stroke event, with an interval between the primary and recurrent events greater than 24 hours; other potential causes of neurological deterioration were excluded. The risk factors for recurrence were analyzed using univariate and logistic regression analyses. A total of 1,021 patients were included in this study with a median length of stay of 14 days (interquartile range,11-18). In-hospital recurrence occurred in 58 cases (5.68%), primarily during the first five days of hospitalization. In-hospital recurrence significantly prolonged the hospital stay (P < 0.001), and the in-hospital mortality was also significantly increased (P = 0.006). The independent risk factors for in-hospital recurrence included large artery atherosclerosis, urinary or respiratory infection and abnormal blood glucose, whereas recurrence was less likely to occur in the patients with aphasia. Our study showed that the patients with AIS had a high rate of in-hospital recurrence, and the recurrence mainly occurred in the first five days of the hospital stay. In-hospital recurrence resulted in a prolonged hospital stay and a higher in-hospital mortality rate.