Introduction <p>Bleomycin-electrosclerotherapy (BEST) is a novel treatment for slow-flow vascular malformations (SFVMs), most studied in venous malformations. This study specifically evaluated its safety and clinical outcome in lymphatic/lymphatic-dominant lympho-venous malformations (LMs/ld-LVMs).</p> Materials and Methods <p>A monocentric cohort with symptomatic LMs or ld-LVMs treated by BEST was retrospectively assessed. A treatment-specific, patient-reported questionnaire assessed overall clinical response (complete response: symptom-free, partial response: improved symptoms, no response: unchanged symptoms, progression of symptoms), subjective health-related quality of life (QoL; optimal, improved, unchanged, worsening), pain (numerical rating scale, NRS), and postprocedural skin discolouration (yes/no). Pre and postprocedural lesion size was measured in three planes on MRI.</p> Results <p>Twenty-seven treatments were performed in 20 patients with 14 LMs and six ld-LVMs (11 microcystic, five mixed, and four macrocystic subtypes). Patients received 1.4 ± 0.6 treatments with a median bleomycin dose of 7&#xa0;mg (range 2–15&#xa0;mg). After BEST, 7/20 (35%) patients reported complete response, 10/20 (50%) partial response, and 3/20 (15%) no response. Health-related QoL was stated as optimal in 10/20 (50%) and as improved in 4/20 (20%) patients. Median pain NRS was reduced from 6 (3–10) to 2 (0–6). Postprocedural skin discolouration occurred in 11/20 (55%) patients. Follow-up MR imaging revealed lesion size reduction from mean maximum volume of 793 cm³ (IQR 155–2199 cm³) to 548 cm³ (IQR 71–1059 cm³). Total complication rate (CIRSE grade 3–4) was 11.1%. No differences in all outcome parameters regarding LMs subtypes were assessed.</p> Conclusion <p>BEST demonstrates efficacy and acceptable safety treating LMs and ld-LVMs, including challenging microcystic lesions previously considered difficult to treat.</p> Level of Evidence <p>3b, Retrospective Cohort Study.</p> Graphical Abstract <p></p>