Pancreatic endometriosis is very rare with only a few cases reported in the literature. The imaging features are non-specific and the definitive diagnosis is usually only established after surgery. We report on a 68-year-old woman with left upper quadrant pain who demonstrated a mass in the pancreatic tail on imaging. Laboratory results showed only mildly elevated liver enzymes, tumor markers were within the normal range. A left pancreatectomy was performed, frozen section suggesting a benign lesion, and final histopathology confirmed endometriotic cysts. A research of the literature found only eight reported cases of endometriotic cysts of the pancreas, with the majority affecting premenopausal women. Preoperative diagnosis is challenging and most patients undergo resection because of suspected neoplasm. Thorough diagnostic workup may help in avoiding extensive surgery and reduce postoperative complications.