Under physiological conditions, the endothelium is a dynamic structure important for maintaining blood vessel tone, regulating blood flow along vessel walls, vascular permeability, coagulation pathways, and leukocyte adhesion. In sepsis, exposure to pathogens and their soluble factors leads to activation of the endothelium, damage to the endothelial glycocalyx (EG), and initiation of numerous mechanisms that play a key role in the development and progression of sepsis. In addition, endothelial dysfunction and damage to the EG result in a potent proinflammatory, procoagulant, proadhesive, and proapoptotic response, leading to dysregulation of vascular tone, increased vascular permeability, increased leukocyte adhesion and migration, and the development of shock and multiorgan failure. In this review, the structure and function of the endothelium and EG are summarized and the mechanisms of their damage during sepsis as well as the consequences of their dysfunction are described. In addition, available knowledge about the methods of detecting endothelial dysfunction and the possibilities of its treatment in sepsis are presented, with the aim of improving the treatment of septic patients.