Background: The aim of this study was to evaluate whether higher serum levels of insulin-like growth factor-I (IGF-I) in the acute phase of ischemic stroke are associated with less severe strokes and better functional outcome in a period of 12-month follow-up.Methods: From October 2014 to August 2015, patients with the diagnosis of acute ischemic stroke admitted to the stroke unit of Firoozgar Hospital, Tehran, Iran, entered this prospective study. National Institutes of Health Stroke Scale (NIHSS) and Modified Rankin Scale (MRS) for stroke scores were used to measure the severity and outcomes of an acute ischemic stroke at the time of admission and 1 year after the stroke, respectively.Results: A total of 60 acute ischemic stroke patients (28 male, 32 female) with the mean age of 71.1 ± 9.0 years were evaluated for the serum level of IGF-I at the time of admission to the stroke unit of Firoozgar Hospital. There was seen a significant correlation between the IGF-I serum level and the MRS scores (P = 0.020; correlation coefficient = −0.32). IGF-I serum level had no significant correlation with NIHSS scores.Conclusion: These results support that the higher serum levels of IGF-I at the time of stroke is associated with a significant better outcome in a 1-year period of follow-up. However, this hormone serum level seems not to have a predictable value for the ischemic stroke severity. Further studies are required to clarify the neuroprotective mechanisms of IGF-I in ischemic stroke process.