Background Tenecteplase has higher fibrin specificity with a longer half-life and the potential to achieve higher rates of recanalization than alteplase. A critical limitation of tenecteplase is no commercial use in Japan and no experience with its administration to Japanese patients. Hypothesis Tenecteplase is superior to alteplase in achieving recanalization on the initial angiogram when administered ≤4.5-hour of stroke onset in patients planned for mechanical thrombectomy (MT) in Japan where alteplase at the unique dose of 0.6mg/kg is officially used. Methods The Tenecteplase versus alteplase For LArge Vessel Occlusion Recanalization (T-FLAVOR) trial is an investigator-initiated, phase II, multicenter, prospective, randomized, open-label, masked-endpoint, superiority study. Eligibility criteria include acute ischemic stroke with pre-stroke modified Rankin Scale score ≤3 and large vessel occlusion (internal carotid artery, middle cerebral artery, or basilar artery) eligible for intravenous thrombolysis ≤4.5-hour and MT ≤6-hour of stroke onset. After completing the safety confirmation phase involving three patients who received non-masked tenecteplase (0.25 mg/kg), 220 patients will be randomized to two groups (1:1), intravenous alteplase (0.6mg/kg, n = 110) or tenecteplase (0.25mg/kg, n = 110), prior to MT. Outcomes In the safety confirmation phase, the primary outcome is symptomatic intracranial hemorrhage (sICH) ≤24-36-hour. In the randomized, comparative phase, the primary efficacy outcome is substantial angiographic reperfusion (mTICI grade 2b/2c/3) or absence of retrievable thrombus on the initial angiogram. The primary safety outcome is sICH ≤24-36-hour and 90-day mortality. Discussion T-FLAVOR may help determine if tenecteplase should be recommended as a routine clinical strategy before MT for Japanese stroke patients. Trial registration jRCTs051210055