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Ventriculoperitoneal shunting (VPS) helps reduce intracranial pressure and alleviate clinical symptoms caused by hydrocephalus in hemorrhagic Moyamoya disease (MMD). To date, no literature describes the occurrence of subdural fluid collection (SDFC) in hemorrhagic MMD patients undergoing VPS prior to cerebral revascularization. This report aims to explore the potential pathological mechanisms underlying SDFC following cerebral revascularization after prior VPS, and to provide effective strategies for future prevention. Clinical data of hemorrhagic MMD patients undergoing VPS prior to bypass admitted to our hospital from 2021 January and 2024 December were selected. Medical records were reviewed to analyze patient characteristics and the entire disease course. Among the 7 patients (9 cases), postoperative SDFC occurred in 7 cases (7/9, 77.8%), located contralateral to the shunt in 6 cases (6/7, 85.7%) and ipsilateral to the surgical side in 1 case (1/7, 14.3%), with onset mostly within 1 day after surgery. Among these 7 patients, 2 underwent subdural drilling and drainage due to significant mass effect caused by the effusion. One of these patients developed herniation with decreased consciousness and notable midline shift, and symptoms gradually improved after subdural drainage. Durin-g short-term clinical follow-up (postoperative period < 12 months), recurrent hemorrhage occurred in 1 out of 9 cases, while no cases of cerebral infarction or seizures were observed. CT angiography (CTA) revealed occlusion of the bypass graft in 2 out of 6 direct bypass cases. Through the findings of this study and literature review, we observe that cerebral revascularization performed during the late phase of VPS may induce SDFC complications through multiple mechanisms. Future implementation of early intervention may effectively reduce the risk of adverse events and improve surgical outcomes.