Platelets play a role in tumor angiogenesis and growth and are the main transporters of several angiogenesis regulators. Here, we aimed to determine the levels of angiogenesis regulators and epithelial-mesenchymal transition factors sequestered by circulating platelets in breast cancer patients and age-matched healthy controls. Platelet pellets (PP) and platelet-poor plasma (PPP) were collected by routine protocols. Vascular endothelial growth factor (VEGF), platelet-derived growth factor BB (PDGF-BB), thrombospondin-1 (TSP-1), platelet factor 4 (PF4), and transforming growth factor-β1 (TGF-β1) were measured by enzyme-linked immunosorbent assay. Angiogenesis-associated expression of VEGF (2.1 pg/106platelets versus 0.9 pg/106platelets,P < 0.001), PF4 (21.2 ng/106platelets versus 10.2 ng/106platelets,P < 0.001), PDGF-BB (42.9 pg/106platelets versus 19.1 pg/106platelets,P < 0.001), and TGF-β1 (15.3 ng/106platelets versus 4.3 ng/106platelets,P < 0.001) differed in the PP samples of cancer and control subjects. In addition, protein concentrations were associated with clinical characteristics(P<0.05). Circulating platelets in breast cancer sequester higher levels of PF4, VEGF, PDGF-BB, and TGF-β1, suggesting a possible target for early diagnosis. VEGF, PDGF, and TGF-β1 concentrations in platelets may be associated with prognosis.