The purpose of this study was to evaluate the effect of a hot water extract from Saccharina japonica (SJH) against oxidation and inflammation in fine dust (FD)-stimulated HaCaT keratinocytes. SJH markedly reduced the production of intracellular reactive oxygen species (ROS) via the activation of nuclear factor erythroid 2-related factor (Nrf)-2/heme oxygenase (HO)-1 signal pathway in FD-stimulated HaCaT keratinocytes. Also, SJH decreased the expression levels of inflammatory initiators such as interleukin (IL)-25, IL33 and thymic stromal lymphopoietin (TSLP), and inflammatory chemokines such as eotaxin, macrophage-derived chemokine (MDC) and thymus and activation regulated chemokines (TARC) in FD-stimulated HaCaT keratinocytes. In addition, SJH effectively downregulated the expression levels of NLR family pyrin domain containing 3 (NLRP3) inflammasome-related molecules including NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1, IL-18 and IL-1b by inhibiting the activation of mitogenactivated protein kinase (MAPK) signaling pathway in FD-stimulated HaCaT keratinocytes. Taken together, these results suggest that SJH has the antioxidant and anti-inflammatory effects in FD-stimulated HaCaT keratinocytes.