Defects in vascular integrity in cerebrovasculature lead to serious pathologies including hemorrhagic stroke. The stability of cell adhesion junctions and actin-myosin contractile machinery are two major determinants for the integrity of endothelial monolayer. Here we have evaluated the protective effects of tanshinone I (Tan I), a lipophilic compound presents in Salvia miltiorrhiza, against atorvastatin-induced cerebral hemorrhage in zebrafish in vivo, and further dissected the molecular mechanisms in HUVECs. We demonstrated that Tan I protected endothelial integrity by stabilizing cell–cell adhesion junctions via the inhibition of Src-mediated VE-cadherin internalization and subsequent junction-linked actin cytoskeleton depolymerization. In addition, Tan I inhibited ROCK-associated endothelial contractile machinery by dephosphorylating cofilin and MYPT1. These findings identified Tan I as an endothelial stabilizing agent and suggested Tan I as a potential treatment for vascular leakage in hemorrhagic stroke.