Hericium erinaceus is an edible mushroom used as a medicinal food in Asian countries. In this study, the chemopreventive effects of H. erinaceus mycelia hot water extract (HEW) were evaluated. HEW remarkably induced the luciferase activity of the antioxidant response element (ARE), located in the promoter region of phase 2 and antioxidant genes and regulated by nuclear factor E2-related factor 2 (Nrf2). The up-regulation of ARE activity by HEW corresponded with the induction of Nrf2 and the antioxidant enzyme, hemeoxygenase-1. The inhibition of cyclooxygenase-2 (COX-2) activity is a promising effective approach in cancer chemoprevention, and HEW prominently suppressed COX-2 protein expression in HepG2 cells. Furthermore, HEW showed anti-inflammatory activity by modulating inflammatory mediators such as nitric oxide (NO), inducible NO synthase, tumor necrosis factor-${alpha}$, interleukin-$1{eta}$, and the transcription factor, nuclear factor-${kappa}B$, in lipopolysaccharide-stimulated RAW 264.7 cells. These results suggest that H. erinaceus possessed anti-tumor and anti-inflammatory effects via the modulation of Nrf2/ARE and inflammatory signaling pathways, and may therefore have potential use as a natural chemopreventive agent.