Although accessory spleen is a frequently encountered entity, accessory spleen in the greater omentum is rare. A 22-year-old woman presented with dull pain in the left upper abdomen. Cross-sectional imaging studies with 3-dimensional reconstruction suggested the presence of a huge tumor in the greater omentum that was associated with the spleen. At laparotomy, the diagnosis of accessory spleen was made. This accessory spleen was unusual in its size and location. Awareness of this entity and familiarity with typical imaging findings is mandatory for preoperative diagnosis. The importance of recognition and appropriate confirmatory diagnosis of an accessory spleen is discussed.