We presented two cases of phyllodes tumor of the breast examined by 99mTc-sestamibi (MIBI) two-phase scintimammography. In the case with malignant phyllodes tumor, 99mTc-MIBI accumulation was recognized on both early and delayed images. In the case with benign phyllodes tumor, however, 99mTc-MIBI accumulation was recognized on only the early image. 99mTc-MIBI delayed imaging may have the potential to distinguish between benign and malignant phyllodes tumors.