In this study, the anti-inflammatory activity and ER stress modulation of the hexane fraction from Peucedanum insolens Kitag. root was investigated. The anti-inflammatory activity was evaluated by measuring nitric oxide inhibition and analyzing iNOS and COX-2 expression in LPS-treated RAW 264.7 macrophages using Western blot. The hexane fraction’s effect on ER stress was assessed by monitoring ATF6α transcriptional activity in the stable recombinant HLR-GV-hATF6α (333) cell line. Additionally, the expression levels of ER stress-related proteins, including eIF2α, p-eIF2α, GRP78, and CHOP, were analyzed by western blot in HeLa cells. Our results demonstrated that the hexane fraction strongly inhibited nitric oxide production and the expression of iNOS and COX-2 in LPS-treated RAW 264.7 cells. It also significantly reduced ATF6α transcriptional activation induced by thapsigargin or tunicamycin. In HeLa cells, the hexane fraction inhibited the expression of ER stress-related proteins GRP78 and CHOP induced by thapsigargin. Although the hexane fraction alone did not affect GRP78, CHOP and eIF2α levels, it enhanced eIF2α phosphorylation in a concentrationdependent manner. Co-treatment with the hexane extract and thapsigargin prevented both CHOP and GRP78 expressions and eIF2α phosphorylation. Taken together, our results suggest that the anti-inflammatory potency of the hexane-fraction of P. insolens might be related to its potential to modulate ER stress. To find out more detailed integrated actions of the hexanefraction of P. insolens against ER stress-induced inflammation signalling and to identify bioactive compound(s) associated with ERSR-related inflammation, further studies are required using a single cell type, such as RAW 264.7 or HeLa cells.