The present disclosure provides antibodies that specifically bind to Mer Tyrosine Kinase (MERTK) (e.g., human MERTK, or both human and mouse MERTK) and compositions comprising such antibodies, wherein said antibody agonizes MERTK signaling on endothelial cells. The present disclosure also provides methods for treating cancer, by administering an antibody that specifically binds to MERTK and agonizes MERTK signaling on endothelial cells.