Background: The potential benefit of intraarterial tenecteplase in acute basilar artery occlusion (BAO) patients with successful reperfusion following endovascular treatment (EVT) has not been studied. Aims: To explore the efficacy and safety of intraarterial tenecteplase in acute BAO patients with successful reperfusion after EVT. Sample size estimates: A maximum of 228 patients are required to test the superiority hypothesis with 80% power according to a two-side 0.05 level of significance, stratified by center. Design: We will conduct a prospective, randomized, adaptive-enrichment, open-label, blinded-end point, multicenter trial. Eligible BAO patients with successful recanalization after EVT [modified Thrombolysis in Cerebral Infarction (mTICI) 2b-3] will be randomly assigned into the experimental and control group with a 1:1 ratio. Patients in the experimental group will receive intraarterial tenecteplase (0.2–0.3 mg/min for 20–30 min), while patients in the control group will receive routine treatment according to the usual practice of each center. Patients in both groups will receive standard guideline-based medical treatment. Outcome: The primary efficacy endpoint is a favorable functional outcome, defined as the modified Rankin Scale 0–3 at 90 days after randomization. The primary safety endpoint is symptomatic intracerebral hemorrhage, defined as National Institutes of Health Stroke Scale score increase ⩾4 caused by intracranial hemorrhage within 48 h after randomization. Subgroup analysis of the primary outcome will be performed by age, gender, baseline NIHSS score, baseline pc-ASPECTS, intravenous thrombolysis, time from estimated symptom onset to treatment, mTICI, blood glucose, and stroke etiology. Conclusions: The results of this study will provide evidence of whether adjunct use of intraarterial tenecteplase after successful reperfusion with EVT is associated with better outcomes for acute BAO patients.