Gossypiboma is an extremely rare adverse event occurring post-surgery, where surgical gauze is left within the body. If aseptically retained, it can lead to the formation of granulation tissue through chronic inflammation and adhesion with surrounding tissues, potentially persisting asymptomatically for many years. While diagnosis of this condition has been reported through various imaging modalities such as abdominal ultrasound and computed tomography, cases not presenting with typical findings are difficult for preoperative diagnosis, and instances where it is discovered postoperatively exist. Particularly when in contact with the gastrointestinal tract within the abdominal cavity, differentiation from submucosal tumors of the digestive tract becomes problematic. This report describes the imaging characteristics of endoscopic ultrasound and the usefulness of endoscopic ultrasound-fine-needle-aspiration for tissue diagnosis in the preoperative diagnosis of intra-abdominal gossypiboma.