Malignant insulinomas are frequently diagnosed at a late stage. Medical management is necessary to slow progression of the disease and control of hypoglycemic symptoms when cure by surgical treatment is not possible. Multimodal treatment, in these cases, has been used with variable clinical response. We describe a 68-yr-old woman who presented response failure to usual treatment and was alternatively treated with radiolabeled metaiodobenzylguanidine ([131I]-MIBG) analogue therapy with development of neurologic complications. We also present a review of the current role of [131I]-MIBG treatment in insulinomas.