Primary adenocarcinoma of the jejunum which accounts for only approximately 3% of all gastrointestinal tract malignancies, is distinctly unusual. Ovarian metastasis from a jejunal cancer is extremely rare. It has significant therapeutic and prognostic implications to differentiate primary ovarian carcinoma from metastatic disease to the ovary. A 49-year-old Japanese woman presented with intermittent nausea, vomiting, and palpable abdominal mass. Pelvic examination and imaging studies revealed a huge ovarian tumor, suspicious for malignancy. Upper GI series and barium enema were unremarkable. Exploratory laparotomy was done for presumed primary ovarian malignancy. Mucinous adenocarcinoma of the right ovary, measuring 25 x 18 x 12 cm, without other intraabdominal dissemination was found. Exploration of the upper abdomen revealed an annular constriction of the jejunum 30 cm distal to the ligament of Treitz. Partial jejunectomy with end-to-end anastomosis was done. Metastatic ovarian cancer from the primary jejunal adenocarcinoma was confirmed microscopically. Although small bowel malignancy is uncommon, small bowel follow-through examination or enteroclysis may be indicated in patients with positive stool for occult blood who have no abnormality in the upper gastrointestinal series and barium enema. In addition to the imaging studies, thorough exploration of the entire abdominal cavity is necessary at ceiliotomy in patients with ovarian malignancy to distinguish primary ovarian cancer from metastatic disease to the ovary.