To examine rates of intravenous thrombolysis (IVT), mechanical thrombectomy (MT), door-to-needle (DTN) time, door-to-puncture(DTP) time, and functional outcome between patients with admission MRI versus CT. Observational cohort study of consecutive patients using a target trial design within the nationwide Swiss-Stroke-Registry from 01/2014 to 08/2020. Exclusion criteria included MRI contraindications, transferred patients, and unstable or frail patients. Multilevel mixed-effects logistic regression with multiple imputation was used to calculate adjusted odds ratios with 95% confidence intervals for IVT, MT, DTN, DTP, and good functional outcome (mRS 0-2) at 90 days. Of the 11049 patients included (mean SD age, 71 15 years; 4811 44% females; 69% ischemic stroke, 16% transient ischemic attack, 8% stroke mimics, 6% intracranial hemorrhage), 3741 (34%) received MRI and 7308 (66%) CT. Patients undergoing MRI had lower NIHSS (median IQR 2 0-6 versus 4 1-11), and presented later after symptom onset (150 versus 123 min, P<.001). Admission MRI was associated with: lower adjusted odds of IVT (aOR 0.83, 0.73-0.96), but not with MT (aOR 1.11, 0.93-1.34); longer adjusted DTN (+22 min 13-30), but not with longer DTP times; and higher adjusted odds of favorable outcome (aOR 1.54, 1.30-1.81). We found an association of MRI with lower rates of IVT and a significant delay in DTN, but not in DTP and rates of MT. Given the delays in workflow metrics, prospective trials are needed to show that tissue-based benefits of baseline MRI compensate for the temporal benefits of CT. This article is protected by copyright. All rights reserved.