Dengue virus (DENV) is the most prevalent arboviral infection, especially in tropical and subtropical regions, affecting millions of people annually. Life-threatening complications of DENV infection include potential hemorrhage and shock. With no specific antiviral treatment currently available for DENV infection, there is an ongoing need for drug development. We have found that the secreted DENV non-structural protein NS1 directly activates myeloid cells via Toll-like receptor 4 (TLR4), inducing inflammatory cytokines and disrupt endothelial cell monolayer disruption in vitro We have demonstrated that inhibition of this activity through natural TLR4 antagonism, LPS-RS, can block NS1 function in vitro and alleviate disease pathology in a murine model. This discovery suggested other TLR4 antagonists could be effective in therapeutic intervention of dengue infection. In this study we explored the potential of one of the leading sepsis candidates to have gone through phase III clinical trials, Eritoran (Eisai Co., Ltd.), as an inhibitor of NS1-mediated TLR4 activation. To investigate the potential of Eritoran for treatment of dengue infection, the inhibitory effects of Eritoran on NS1-mediated responses induced in vitro were assessed in PBMC and endothelial cell monolayer. In addition, the AG129 mouse model of dengue infection was used to confirm the effect of Eritoran for survival and vascular leakage. We demonstrated that Eritoran potently inhibited DENV NS1 stimulated IL-6 production in PBMCs. The drug also inhibited NS1-mediated monolayer disruption in vitro. Intravenous and intraperitoneal injection of Eritoran starting from day 2 post-infection, but not a pre-treatment regimen, improved survival to 60% and 40%, respectively, at day 8 post infection. Interestingly, viral loads were significantly reduced by all treatments compared to the matched control groups. Eritoran therapy also reduces dengue-induced vascular leakage. These results suggest that Eritoran blockade of NS1 induced responses represents a novel therapeutic approach for DENV treatment.