Paxillin is a focal adhesion adaptor protein essential for cell adhesion and migration, regulated by reversible phosphorylation. In endothelial cells, phosphorylation at serine 126 (Ser126) plays a key role in processes like angiogenesis and vascular permeability. This study aimed to identify the phosphatase responsible for dephosphorylating Ser126, a previously unexplored mechanism. Using recombinant paxillin and in vitro kinase assays, we confirmed that PKC phosphorylates Ser126. Inhibition studies in endothelial cells revealed that calcineurin mediates Ser126 dephosphorylation. Phosphorylation at Ser126 enhances paxillin localization to focal adhesions, suggesting a dynamic regulatory mechanism in endothelial cell signaling.