Long COVID is associated with persistent neurological symptoms. Among the proposed mechanisms, several vascular hypotheses such as endothelial dysfunction, microthrombosis, and impaired cerebral autoregulation, have been suggested as potential contributors to these long-term effects. In this cross-sectional study, we used arterial spin labeling (ASL) MRI to investigate global and regional perfusion alterations in 186 participants (145 with Long COVID and 41 healthy controls) approximately two years post-infection. Structural and ASL MRI data were processed with the ExploreASL pipeline to derive cerebral blood flow (CBF) and the spatial coefficient of variation (sCOV), a quantitative proxy for arterial transit time (ATT) and an indirect marker of global vascular dysfunction. A multiple linear regression model revealed significantly higher global gray matter sCOV in Long COVID patients (p = 0.02), independent of age, sex, and white matter hyperintensity (WMH) volume. At the lobar level, an ANCOVA adjusted for age, sex, and WMH volume showed consistently elevated sCOV in multiple regions, with the left insula remaining significant after FDR correction (p = 0.01). No significant differences were found in regional CBF or WMH volume. These results point to increased sCOV as a potential early indicator of diffuse vascular dysregulation in Long COVID, reinforcing the need to consider delayed ATT and systemic cerebrovascular effects in Long COVID neuroimaging research.