We report here on a case of invasive ductal carcinoma arising in a recurrent malignant phyllodes tumor. The patient was a 33-year-old woman who presented with a left breast mass, and an excision was then performed. The mass, measuring 7.0 x 4.0 cm in size, was relatively well demarcated with a nodular contour and showed pale gray and solid cut surface with clefts on it. Histologically, the mass mainly consisted of stromal components that were characterized by high cellularity, marked nuclear atypism and brisk mitosis. The sparse glandular components were leaf-like in shape and lined by bland ductal epithelium without any nuclear atypism. Sixteen months later, the patient revisited our hospital with a recurrent mass, and underwent total mastectomy. The recurrent mass contained foci of definite invasive ductal carcinoma in the background of malignant phyllodes tumor, which was identical to the primary mass. This case demonstrates that it is possible that an invasive ductal carcinoma might arise within, at least with, a recurrent malignant phyllodes tumor.