Designated for cyclic shedding, the endometrial stroma is rich in endometrial mesenchymal stem cells (EMSCs) and may play an important role in the development of endometrial carcinoma (EC). This study characterized the crosstalk of EC cells with EMSCs and the resultant effects on malignant phenotypes. The cultured EMSCs expressed CD73, CD90, and CD105, but not CD14, CD19, CD34, CD45, or human leukocyte antigen-antigen D related markers. These EMSCs also showed osteogenic, adipogenic, and chondrogenic differentiation ability. Transforming growth factor (TGF)-β1 and C-X-C motif chemokine ligand 12 (CXCL12) secretion or expression were reciprocally enhanced in EC cells and EMSCs, as well as in their tissues. By acting on the receptors expressed in their mutual target cells, the interaction between TGF-β and CXCL12 results in the enhanced migration, invasion, tumorigenesis, and epithelial-mesenchymal transition of EC cells, which can be blocked by neutralizing the antibody of either CXCL12 or C-X-C chemokine receptor type 4. The study revealed unprecedented paracrine interactions between EC cells and EMSCs that resulted in the enhancement of transformation phenotypes. Thus, the blocking of TGF-β or CXCL12 signaling can be a therapeutic target for EC.