Sister Mary Joseph's nodule refers to palpable nodules bulging into the umbilicus as a result of metastasis from malignancy in the abdomen or pelvis. The most common primaries are in the gastrointestinal or genital tract, while other origins are considered rare. We recently treated a 71-year-old man who presented with painless umbilical swelling. Further investigation, including laboratory, radiological and histopathological exam, confirmed the diagnosis of a metastatic neuroendocrine tumor. The peculiarity of this case is that the umbilical swelling was the initial presentation of a neuroendocrine tumor and, to our knowledge, this is the first to be reported. This case demonstrates that neuroendocrine tumor is a rare cause of Sister Mary Joseph's nodule.