The objective of the study was to investigate the mechanisms of insufficient interferon-γ (IFN-γ) response to interleukin 18 (IL-18) and the treatment for the insufficient response in septic mice. Interleukin 18 stimulation does not restore IFN-γ production by blood mononuclear cells in septic patients but does restore its production in postoperative patients. Although sepsis impairs the IFN-γ response to IL-18, little is known about why the IL-18/IFN-γ-mediated immune response is ineffective in patients with sepsis. A cecal ligation and puncture was made in C57BL/6 mice following a sublethal lipopolysaccharide challenge to examine their IFN-γ response to IL-18, focusing on natural killer (NK) cells and cytokines. We next examined the effect of neutralization of IL-10 on the NK cell and survival in septic mice. Interleukin 18 injection did not restore IFN-γ production in septic (cecal ligation and puncture) mice. Despite an increase in the numbers of liver NK cells, the IL-18 receptor (IL-18R) expression was decreased in the septic mice compared with sham mice. Serum IL-10 levels were positively correlated with the percentage of liver NK cells, but negatively with their IL-18R expression. Neutralization of IL-10 restored the IL-18R expression on liver NK cells and restored the IFN-γ response in the septic mice, improving their survival. Sepsis might impair IL-18R expression on liver and spleen NK cells and impair the IL-18-mediated IFN-γ response. Neutralization of IL-10 may restore this response in septic hosts, thereby improving survival.