Malignant ascites is a frequent complication in oncological diseases. There are no standard therapies for any primary tumour. We report the case of a woman, aged 49 years at the time of primary diagnosis, who suffered from recurrent ascites resulting from liver metastasis of breast cancer. Based on the literature and former experience of our department, mistletoe extract was repeatedly applied intraperitoneally at the occasion of decompressive punctures. The further course of the disease suggests a significant role of mistletoe in achieved symptom control, which also resulted in a considerable improvement in quality of life. The mistletoe solution was well tolerated. Relevant mechanisms of action in addition to the well-known immunomodulating properties of mistletoe could be direct cytotoxic and adjuvant effects to the concomitantly administered chemotherapy of carboplatin/paclitaxel.