Platelet IL-1α drives cerebrovascular inflammation. Our data suggest that platelet-derived IL-1α induces the activation of cerebrovascular endothelial cells. The expression of brain endothelial cell adhesion molecules (CAMs) and release of the chemokine CXCL1 are induced by platelet IL-1α. In addition, platelet-derived IL-1α supports the TEM of neutrophils. We propose that platelet IL-1α is a key contributor to cerebrovascular inflammation, permitting the brain infiltration of neurotoxic white blood cells.