Objective: The term “weekend effect” refers to an increase in the mortality rate for hospitalizations occurring on weekends versus weekdays. In this study, we investigated whether such an effect exists in patients undergoing mechanical thrombectomy for acute ischemic stroke with large vessel occlusion (currently the standard treatment for this condition) at a single center in Japan. Methods: We surveyed 151 patients who underwent mechanical thrombectomy for acute ischemic stroke with large vessel occlusion (75 and 76 patients were treated during daytime and nighttime, respectively) from January 2019 to June 2021. The items evaluated in this analysis were the rate of modified Rankin Scale ≤2 or prestroke scale, mortality, and procedural treatment time. Results: The rates of modified Rankin Scale ≤2 or prestroke scale and mortality at 90 days after treatment did not differ significantly between daytime and nighttime (41.3% vs. 29.0%, p=0.11; 14.7% vs. 11.8%, p=0.61, respectively). The door-to-groin time tended to be shorter during daytime versus nighttime (57 [IQR: 42.5–70] min vs. 70 [IQR: 55–82]) min, p=0.0507). Conclusions This study did not reveal differences in treatment outcome between daytime and nighttime in patients undergoing mechanical thrombectomy for acute ischemic stroke with large vessel occlusion. Therefore, the “weekend effect” was not observed in our institution.