A 35-year-old man with a history of blunt abdominal trauma and splenic rupture was diagnosed with an ampullary adenocarcinoma. At workup, a CT scan showed multiple intra-abdominal lesions similar to peritoneal carcinosis, and the patient was referred for palliative chemotherapy. On clinical suspicion, however, a biopsy was performed on an intra-abdominal lesion, establishing the diagnosis of abdominal splenosis. A radical pancreaticoduodenectomy ad modum Whipple was performed, followed by adjuvant chemotherapy with gemcitabine. At the 18-month follow-up, the patient was free from recurrent disease. We conclude that splenosis should be considered as a differential diagnosis of peritoneal metastases in cancer patients with a history of abdominal trauma and/or splenectomy. Other reports on splenosis in cancer patients and diagnostic workup are discussed.