Appendiceal cancer associated with pseudomyxoma peritonei is a relatively low-grade malignancy rarely associated with extraperitoneal metastasis. We report herein the case of a 71-year-old man in whom a metastasis was found in the stomach 2 years after he underwent surgery for pseudomyxoma peritonei of appendiceal cancer. He was referred to our hospital after presenting with anorexia and vomiting. Gastrofiberscopy, abdominal computed tomography, and ultrasound examination all revealed a mass 4 × 4 cm in size, containing a small ulcer, in the antrum of the greater curvature of the stomach. The histopathological diagnosis made from a biopsy of the tumor was mucinous cystadenocarcinoma. A distal partial gastrectomy was performed and the resected specimens from the appendiceal cancer resected 2 years earlier showed the same histological pattern as that of the gastric lesion. To the best of our knowledge, this is only the second report of pseudomyxoma peritonei secondary to mucinous cystadenocarcinoma of the appendix that metastasized to the stomach.