The observation that the architecture of the cardiovascular and nervous systems is drawn by common guidance cues and the closeness between neural progenitors and endothelial cells in the vascular niche strongly suggests the existence of links between endothelial and neural cell fates. We identified an embryonic stem cell-derived discrete, nonclonal cell population expressing the two vascular endothelial growth factor receptors neuropilin-1 (Nrp1) and Flk1 that differentiates in vitro toward endothelial or neural phenotypes depending on microenvironmental cues. When microinjected in the chick embryo, Nrp1⁺ cells integrate within the host, developing vessels and brain, and acquire endothelial and neural markers, respectively. These results show that precursors of endothelial cells and precursors of neural cells arise from the same pool of differentiating embryonic stem cells and share the expression of Nrp1 and Flk1. These data reinforce the parallelism between vascular and nervous system at the level of cell fate and commitment and open new perspective in regenerative medicine of neurovascular diseases.—Gualandris, A., Noghero, A., Geuna, M., Arese, M., Valdembri, D., Serini, G., Bussolino, F. Microenvironment drives the endothelial or neural fate of differentiating embryonic stem cells coexpressing neuropilin-1 and Flk-1.