The purpose of this study was to evaluate the inhibitory effects of a hot water extract from Saccharina japonica (SJH) against fine dust (F.D)-induced skin inflammation in human keratinocytes (HaCaT). SJH markedly improved the cell viability decreased by F.D stimulation without any cytotoxicity. In addition, SJH decreased the generation of nitric oxide (NO) in F.D-stimulated HaCaT keratinocytes. Moreover, SJH reduced the expression levels of inflammatory cytokines such as interleukin (IL)-1β, IL-5, IL-6, IL-8 and tumor necrosis factor (TNF)-α decreasing the protein expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), the pro-inflammatory mediators. Interestingly, SJH effectively inhibited the activation of nuclear factor (NF)κB signaling pathway in F.Dstimulated HaCaT keratinocytes. Taken together, these results suggest that SJH effectively suppresses the skin inflammation induced by F.D stimulation.