Abstract: The authors reported the disease development process, clinical manifestations, laboratory tests, and conventional imaging examinations results in a rare case of gastric adenocarcinoma patient with rectal and cervical metastasis detected by ¹⁸F-fluorodeoxyglucose (FDG) PET/CT examination after surgery, and finally accurately detected tumor lesions through ¹⁸F-FDG PET/CT examination. The biopsy results confirmed rectal and cervical metastasis of gastric adenocarcinoma, indicating that ¹⁸F-FDG PET/CT has important value in evaluating the recurrence and metastasis of gastric cancer after surgery.