Surgical treatment of craniopharyngioma often leads to a rapid and dramatic weight gain, leading to hypothalamic obesity. Treatment focused on the diet, physical activity, and different types of drugs have very often provided unsatisfactory results. To date, no data have been reported on hypothalamic obesity (HO) regarding the use of semaglutide, a novel type 1 receptor glucagon-like peptide-1 agonist, to limit body weight gain after surgical removal of a neoplasm, despite its already documented efficacy in obesity treatment. In this case report, we tested semaglutide in an 18-year-old patient with HO induced by a surgical intervention for craniopharyngioma. A very favorable treatment response was found in terms of body weight reduction and improvement in metabolic parameters. Our patient lost more than than 30 kg after only 6 months of therapy, which has never been reported before in the literature on HO.