Small bowel tumors are very rare and generally malignant. As a result of the anatomical location and nonspecific manifestations of small bowel tumors, they are very difficult to diagnose. Balloon-assisted enteroscopy is a relatively noninvasive method compared to surgical resection, and allows for real-time observation, tissue confirmation with biopsy, and interventional procedures. Here, we report the case of a 69-year-old woman with a small bowel metastatic carcinoma observed with double balloon enteroscopy (DBE). She had a history of multiple cancers including ovarian cancer, bladder cancer, and breast cancer. The antegrade DBE procedure was performed before surgery for biopsy tissue confirmation. The patient underwent small bowel resection, and the final diagnosis was the same as that determined by preoperative biopsy. The final diagnosis was metastatic small bowel cancer originating from a cancer of the breast. This is the first detailed report of the preoperative diagnosis of small intestinal metastatic breast cancer by DBE.