To explore the possible relation between collateral circulation and curative effects and clinical outcomes in patients with acute cerebral infarction after mechanical thrombectomy. Methods: A total of 31 patients with acute cerebral infarction who received mechanical thrombectomy were retrospectively analyzed. The status of collateral circulation of patients was hierarchically evaluated to divide patients into the good collateral circulation group and poor collateral circulation group. The curative effects were determined according to NIHSS score. The clinical outcomes, such as good outcome (0～2 points) or poor outcome (3～5 points), were determined based on the mRS score at day 90. Multiple Logistic regression analysis was used to study the effects of collateral circulation on the clinical outcome after mechanical thrombectomy. Results: There was no statistically significant difference in the baseline NIHSS score between the good collateral circulation group and poor collateral circulation group (P=0.055), but there was a significant difference in NIHSS score between the two groups at day 15 (P=0.004). Among the 31 patients, 17 cases had good outcomes and 14 cases had poor outcomes. Baseline NIHSS score (P=0.044) and collateral circulation score (P=0.021) were important influencing factors of clinical outcomes. Conclusion: Among patients with acute cerebral infarction who received mechanical thrombectomy, those with good collateral circulation are more likely to achieve improvement of neurological function. Collateral circulation score and baseline NIHSS score may have a certain correlation with clinical outcomes.