Abstract: The authors reported a case of breast metastasis of gastric adenocarcinoma with ¹⁸F-FDG PET/CT imaging, and analyzed the disease characteristics from clinical symptoms, manifestation of ¹⁸F-FDG PET/CT imaging, pathological diagnosis and differential diagnosis. As the breast metastasis of gastric adenocarcinoma was rare with a non-specific clinical manifestation, it is easy to be missed and misdiagnosed. The disease diagnosis depended on histopathological examination. ¹⁸F-FDG PET/CT imaging of total body can detect primary tumor and metastases in an early stage and improve the accuracy of diagnosis.