Background and Purpose The European Cooperative Acute Stroke Study (ECASS) III showed that intravenous recombinant tissue plasminogen activator (rtPA) administered in the 3 to 4.5 h after symptom onset significantly improved clinical outcomes in patients with acute ischemic stroke (AIS). But little is known regarding the safety and efficacy of intravenous rtPA treatment within this extended time window in Chinese patients with AIS. Methods and Results Data were collected from the Thrombolysis Implementation and Monitor of acute ischemic Stroke in China (TIMS-China). A total of 574 patients who underwent rtPA therapy within 4.5 h after symptom onset were included in this study: 409 in the 0- to 3-h group and 165 in the 3- to 4.5-h group. There were no significant differences in SICH rate (2.4% vs. 1.5%, P = 0.70) at 24 to 36 h, mortalities (7.5% vs. 7.3%, P = 0.84), independence rate (68.9% vs. 63.9%, P = 0.19), and excellent recovery rate (60.9% vs. 52.4%, P = 0.11) between the two time window groups. These results were comparable with previous Western studies. Conclusion This study suggests that intravenous rtPA treatment at 3 to 4.5 h of symptom onset remains safe and effective in Chinese patients with AIS.