A yolk sac tumor is a rare malignant germ cell tumor that typically originates from gonads, though it can arise from an extragonadal location. A rare case of an extragonadal yolk sac tumor in a 32-year-old woman with peritoneal and omental dissemination and liver metastases is reported. The patient’s serum AFP level was elevated. Contrast-enhanced computed tomography (CT) showed an enhanced mass in the posterior cul-de-sac with dilated internal vessels. On magnetic resonance imaging (MRI), flow voids were seen within the mass on T2-weighted imaging, and multiple peritoneal nodules and liver metastases were also evident. Pathological examination showed a yolk sac tumor, and chemotherapy was started. This case showed all four CT signs previously described as suggestive of yolk sac tumor: mixed solid-cystic nature, intratumoral hemorrhage, marked enhancement, and dilated intratumoral vessel. Yolk sac tumors are common in young women and are known for their chemosensitivity. Therefore, prompt diagnosis is important to allow prompt treatment. The combination of clinical and imaging findings contributed to the preoperative diagnosis of yolk sac tumor in the present case and allowed prompt treatment and a surgical plan.