We investigated the hypothesis that the administration of dehydrocostuslactone (DL), a sesquiterpene lactone found in Saussurea lappa Clarke (Compositae), might reduce organ failure and increase survival in a cecal ligation and puncture (CLP)-induced mouse model of sepsis due to HO-1 induction. Treatment of RAW264.7 cells with DL increased HO-1 expression in a time- and concentration-dependent manner, and this up-regulation of HO-1 by DL was significantly inhibited by silencing either Nrf2 and p38 or treating cells with SB203580 (a p38MAPK inhibitor), but it was not inhibited in the presence of SP600125 (an ERK inhibitor), PD98059 (a JNK inhibitor), or LY294002 (PI3K inhibitor). As expected, DL concentration dependently inhibited the expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2), and the productions of NO and PGE2 in LPS-activated cells, and these inhibitions were reversed by silencing HO-1. Most importantly, administration of DL significantly reduced mortality and reduced serum IL-1β and TNF-α and the infiltration of macrophages into liver tissues of CLP-mice. Inducible NOS expression in lung and liver tissues of CLP-mice was reduced by DL, which was reversed by the co-administration of zinc-protoporphyrin IX (ZnPPIX; a competitive inhibitor of HO-1). Our findings indicate that DL might be useful for the treatment of sepsis.