Benign multicystic mesothelioma is a rare tumour that originates from the abdominal peritoneum with a predisposition to the pelvic peritoneum. It typically affects women of reproductive age. There have been less than 200 cases of this rare neoplasia reported to date. We present the case of a 35-year-old woman who was referred to our centre because of the detection of a peritoneal carcinomatosis during a gynaecological exam. A diagnostic laparoscopy was performed. The findings included multiple cysts appearing as 'a bunch of grapes' occupying the omentum. Biopsies were taken during the surgery and the results showed benign multicystic peritoneal mesothelioma. Benign multicystic mesothelioma can simulate other conditions, such as malignant ovarian tumours or cystic lymphangioma. It is often diagnosed accidentally during surgery performed for another reason. The diagnosis is interoperative, observing multicystic structures grouped as a 'bunch of grapes' containing clear fluid with thin walls made of connective tissue. Immunohistochemistry confirmed mesothelial origin. Surgery is considered the treatment of choice and is based on the removal of the cysts from the abdominal cavity. Hyperthermic intraperitoneal chemotherapy can be considered as a primary treatment in patients with recurrences or even as a part of primary treatment associated with surgery. Survival at 5 years is 100% and invasive or malignant progression is extraordinary. The treatment approach should be multidisciplinary, and the patient should be referred to a referral centre.