Canine Vascular Endothelial Growth Factor A (VEGF-A) is a member of the vascular endothelial growth factor (VEGF) family, which includes VEGF-A, VEGF-B, VEGF-C, VEGF-D, and placental growth factor (PlGF)—key regulators of angiogenesis, vascular development, and endothelial cell function. In dogs (Canis lupus familiaris), VEGF-A is produced by a variety of cell types including endothelial cells, macrophages, fibroblasts, epithelial cells, and tumor cells, particularly in response to hypoxia, inflammation, or tissue injury. VEGF-A exerts its biological effects primarily through binding to VEGF receptor-1 (VEGFR-1/Flt-1) and VEGF receptor-2 (VEGFR-2/KDR) on endothelial cells, activating intracellular signaling pathways such as MAPK/ERK, PI3K/AKT, and PLCγ, which promote endothelial cell proliferation, migration, vascular permeability, and formation of new blood vessels. In canine physiology, VEGF-A plays important roles in normal vascular development, wound healing, and tissue regeneration. Dysregulated VEGF-A expression is also associated with tumor angiogenesis in canine cancers, including hemangiosarcoma, mammary tumors, mast cell tumors, and osteosarcoma, where increased VEGF signaling supports tumor growth and metastasis by promoting blood vessel formation. Because dogs develop many spontaneous cancers similar to those in humans, canine VEGF-A is widely studied in veterinary oncology, angiogenesis research, and comparative cancer biology, contributing to understanding of vascular growth mechanisms and potential anti-angiogenic therapeutic strategies.