In this Letter, we first investigated the barrier protective effects of eckol and itsderivatives against pro-inflammatory responses in human umbilical vein endothelial cells (HUVECs) and in mice. Data showed that eckol (1) and dieckol (2) inhibited lipopolysaccharide (LPS)-mediated barrier disruption and transendothelial migration of leukocytes to human endothelial cells. Eckol (1) also suppressed