The patient was a 66-year-old woman. An induration of approximately 15 mm in size that accompanied redness was palpable in the umbilical fossa. She did not respond to 1-month antibiotic treatment provided by the previous physician. For this reason, a biopsy of the site was performed with the possibility of neoplastic disease in mind, resulting in the detection of adenocarcinoma. Subsequent detailed whole-body examination revealed advanced gastric cancer and peritoneal dissemination, and the induration in the umbilical fossa was diagnosed as a direct infiltration from the peritoneal dissemination. Metastasis or infiltration of malignant tumor to the umbilicus is called Sister Mary Joseph's nodule (SMJN), and considered as a sign of poor prognosis. However, this case was successfully treated and achieved a long-term prognosis by the early diagnosis of SMJN. In routine clinical practice, it is considered necessary to examine patients carefully, as not to overlook SMJN.