The present study was designed to investigate the effect of chloroform fraction of Sargassum horneri methanol extract (SHMC) against skin barrier damage and skin moisture reduction in UVB-irradiated keratinocytes. SHMC increased the cell viability by reducing the intracellular ROS production without cytotoxicity in UVB-irradiated keratinocytes. In addition, SHMC activated the nuclear factor erythroid 2-related factor 2 (Nrf2)/NAD(P)H dehydrogenase [quinone]-1 (NQO-1)/heme oxygenase-1 (HO-1) signaling pathway. Interestingly, the inhibition of HO-1 attenuaed the increment of cell viability, the reduction of intracellular ROS production and the inhibition of NFκB activation induced by SHMC. Moreover, SHMC recovered the skin barrier damage and the skin moisture reduction by regulating the expression level of nucleotide-binding oligomerizatin domain (NOD)-like receptor containing pyrin domain 3 (NLRP3, cryopyrin) inflammsome signaling. Collectively, these results suggest that SHMC improved the skin barrier and the skin moisturization in UVB-irradiated keratinocytes.