Purpose <p>To review the available evidence on the effectiveness and safety of bleomycin electrosclerotherapy (BEST) for slow-flow vascular malformations.</p> Materials and Methods <p>A systematic review was conducted according to PRISMA guidelines, with a protocol registered in PROSPERO. Five databases were searched, supplemented by citation tracking, to identify peer-reviewed studies reporting clinical outcomes of BEST for slow-flow vascular malformations. Single-patient case reports were excluded. Two authors independently extracted data and assessed risk of bias.</p> Results <p>Ten studies were included, with a total of 401 patients and 416 lesions. Seven studies were retrospective, three were prospective, and one was comparative. Any symptom improvement was reported in 62–100% of patients; however, outcome definitions and assessment methods varied substantially across studies, limiting direct comparability. Any size reduction was reported in 83–100% of lesions, based on clinical and imaging-based assessments, including volumetry. Serious adverse events were uncommon, and no systemic toxicity was reported. All non-randomised studies had serious risk of bias.</p> Conclusion <p>BEST appears promising for selected slow-flow vascular malformations. However, evidence is limited by methodological heterogeneity and high risk of bias, and treatment decisions should remain individualised and based on multidisciplinary evaluation.</p> Graphical Abstract <p></p>