Angiogenesis is a key in cancer progression and its regulators are released both by the tumor cells and the stroma. Dietary phytoestrogens, such as the lignan enterolactone (ENL) and the isoflavone genistein (GEN), may differently affect breast cancer growth. In this study, human breast cancer cells (MCF-7) were established in mice creating a tumor with species-specific cancer and stroma cells. Ovariectomized athymic mice supplemented with estradiol (E2) were fed basal AIN-93G diet (BD) or BD supplemented with 100 mg/kg ENL, 100 mg/kg GEN or their combination (ENL+GEN). We show that ENL and ENL+GEN inhibited E2-induced cancer growth and angiogenesis, whereas GEN alone did not. Microdialysis was used to sample extracellular proteins in tumors in vivo. ENL and ENL+GEN decreased both stroma- and cancer cell-derived VEGF, whereas cancer cell-derived PlGF increased. In subcutaneous Matrigel plugs in mice, ENL and ENL+GEN decreased E2-induced endothelial cell infiltration, whereas GEN alone did not. In endothelial cells, ENL inhibited E2-induced VEGFR-2 expression, whereas GEN did not. These results suggest that ENL has potent effects on breast cancer growth, even in combination with GEN, by downregulating E2-stimulated angiogenic factors derived both from the stroma and the cancer cells, whereas dietary GEN does not possess any antiestrogenic effects.