Peritoneal mucinous carcinomatosis is an aggressive subtype of pseudomyxoma peritonei, which often leads to inoperable bowel obstruction and, ultimately, death. Due to the poor prognosis, treatment is often symptomatic and aimed at alleviating the symptoms - pain, nausea, and vomiting - associated with gastrointestinal obstruction. Due to their antisecretory activity, somatostatin analogues are commonly prescribed in such cases. In the case presented here, a patient diagnosed with disseminated peritoneal mucinous carcinomatosis of appendiceal origin responded well to symptomatic treatment with lanreotide Autogel(®) at a dose of 120 mg/28 days. More importantly, radiological evidence of a reduction in peritoneal ascites, indicative of antiproliferative activity, was observed. These findings are important, particularly given the negative impact of this disease on both quality of life and survival. This case adds to the growing body of evidence supporting the antiproliferative and antisecretory activity of lanreotide Autogel.