Pseudomyxoma peritonei (PMP) is a rare disease that usually originates from mucinous neoplasms of the appendix and, less commonly, from extra-appendiceal tumors, but it may also be caused by synchronous primary mucinous tumors of the ovary and appendix. The current study discusses the case of a 73-year-old female who presented with progressively worsening indigestion and abdominal distension. Magnetic resonance imaging of the pelvis revealed a large cystic mass with a thin enhancing septa arising from the right ovary and ascites with scalloping of the liver surface. On laparotomy, the patient was observed to have a large ruptured mass on the right ovary and a partially amputed distended appendix filled with mucin. The subsequent pathology report confirmed a borderline mucinous tumor of the right ovary and a low-grade appendiceal mucinous neoplasm associated with PMP. Immunohistochemical examination demonstrated the ovarian tumor stained strongly positive for cytokeratin (CK)-7, and negatively for CK-20 and homeobox protein CDX-2 (CDX2), whereas the appendiceal tumor stained negative for CK-7 and positive for CK-20 and CDX2. This study presents a rare case of PMP caused by synchronous primary mucinous tumors of the ovary and appendix in a postmenopausal female.