Background Little is known about the implications for revascularization success of target vessel occlusions (TVOs) with persisting antegrade perfusion before initiation of endovascular stroke treatment (EST) (modified treatment in cerebral ischemia (mTICI 1)) compared to a complete occlusion (mTICI 0). Here, we compared these two states of TVO. Methods Retrospective, single-center analysis of patients treated for M1-segment middle cerebral artery (MCA) occlusion with EST from January 2015 until May 2020 in a tertiary stroke center. Primary study endpoint was successful recanalization (mTICI 2c-3) after one thrombectomy attempt. Secondary endpoints were clinical outcome (modified Rankin Scale (mRS) 90 days after stroke onset), complication rate, and rate of underlying atherosclerotic disease. The two study groups were compared in univariate analysis including patient characteristics and procedural details. Results In this study, 422/581 patients (72.6%) presented with complete M1-occlusion compared to 159/581 (27.4%) with incomplete M1-occlusion. Neither did the recanalization success rate differ between the study groups nor the rate of complications (mTICI 0: 2.4%, mTICI 1: 0.6%, p = 0.304) or underlying atherosclerotic disease. Patients with incomplete initial occlusion showed a lower mRS at discharge (median interquartile range (IQR) mTICI 0: 4 (3–5) vs. mTICI 1: 3 (2–6), p = 0.014), but a comparable mRS 90 days after stroke onset (mTICI 0: 3 (2–6) vs. mTICI 1: 4 (2–6), p = 0.479). Conclusion Complete M1-occlusions (mTICI 0) and incomplete occlusions (mTICI 1) show the same recanalization success, comparable complication rate, and clinical outcome as well as the same rate of underlying atherosclerotic disease. Thus, incomplete M1-occlusions do not allow for an individualized interventional approach.