Background: Admission hyperglycemia impairs outcome in acute ischemic stroke (AIS) patients undergoing mechanical thrombectomy (MT). Since hyperglycemia in AIS represents a dynamic condition, we tested whether the dynamic patterns of hyperglycemia, defined as blood glucose levels > 140 mg/dl, affect outcomes in these patients. Methods: We retrospectively analyzed data of 200 consecutive patients with prospective follow-up. Based on blood glucose level, patients were distinguished into 4 groups: (1) persistent normoglycemia; (2) hyperglycemia at baseline only; (3) hyperglycemia at 24-h only; and (4) persistent (at baseline plus at 24-h following MT) hyperglycemia. Results: AIS patients with persistent hyperglycemia have a significantly increased risk of poor functional outcome (OR 6.89, 95% CI 1.98–23.94, p = 0.002, for three-month poor outcome; OR 11.15, 95% CI 2.99–41.52, p = 0.001, for no major neurological improvement), mortality (OR 5.37, 95% CI 1.61–17.96, p = 0.006, for in-hospital mortality; OR 4.43, 95% CI 1.40–13.97, p = 0.01, for three-month mortality), and hemorrhagic transformation (OR 6.89, 95% CI 2.35–20.21, p = 0.001, for intracranial hemorrhage; OR 5.42, 95% CI 1.54–19.15, p = 0.009, for symptomatic intracranial hemorrhage) after endovascular treatment. These detrimental effects were partially confirmed after also excluding diabetic patients. The AUC-ROC showed a very good performance for predicting three-month poor outcome (0.76) in-hospital mortality (0.79) and three-month mortality (0.79). Conclusions: Our study suggests that it is useful to perform the prolonged monitoring of glucose levels lasting 24-h after MT.