Apoptosis‐associated speck‐like protein containing a caspase recruitment domain (ASC), an adaptor protein for inflammasome receptors, is essential for inducing caspase‐1 activation and the consequent secretion of interleukin‐1β (IL‐1β), which is associated with local inflammation during liver ischemia/reperfusion injury (IRI). However, little is known about the mechanisms by which the ASC/caspase‐1/IL‐1β axis exerts its function in hepatic IRI. This study was designed to explore the functional roles and molecular mechanisms of ASC/caspase‐1/IL‐1β signaling in the regulation of inflammatory responses in vitro and in vivo. With a partial lobar liver warm ischemia (90 minutes) model, ASC‐deficient and wild‐type mice (C57BL/6) were sacrificed at 6 hours of reperfusion. Separate animal cohorts were treated with an anti–IL‐1β antibody or control immunoglobulin G (10 mg/kg/day intraperitoneally). We found that ASC deficiency inhibited caspase‐1/IL‐1β signaling and led to protection against liver ischemia/reperfusion (IR) damage, local enhancement of antiapoptotic functions, and down‐regulation of high mobility group box 1 (HMGB1)–mediated, toll‐like receptor 4 (TLR4)–driven inflammation. Interestingly, the treatment of ASC‐deficient mice with recombinant HMGB1 re‐created liver IRI. Moreover, neutralization of IL‐1β ameliorated the hepatocellular damage by inhibiting nuclear factor kappa B (NF‐κB)/cyclooxygenase 2 signaling in IR‐stressed livers. In parallel in vitro studies, the knockout of ASC in lipopolysaccharide‐stimulated bone marrow–derived macrophages depressed HMGB1 activity via the p38 mitogen‐activated protein kinase pathway and led to the inhibition of TLR4/NF‐κB and ultimately the depression of proinflammatory cytokine programs. Conclusion: ASC‐mediated caspase‐1/IL‐1β signaling promotes HMGB1 to produce a TLR4‐dependent inflammatory phenotype and leads to hepatocellular injury. Hence, ASC/caspase‐1/IL‐1β signaling mediates the inflammatory response by triggering HMGB1 induction in hepatic IRI. Our findings provide a rationale for a novel therapeutic strategy for managing liver injury due to IR. (HEPATOLOGY 2013)