Dysregulated activation of inflammation is associated with the development and progression of many diseases. Generation of reactive oxygen species (ROS) has been shown to promote an inflammatory response. Cathelicidin peptides not only defend against the invasion of various microbes but also play an important role in regulating immune responses. The objective of this study was to investigate the effects and mechanisms of Cathelicidin-WA (CWA) on the inflammatory response and oxidative stress in macrophages. Our results showed that CWA efficiently attenuated lipopolysaccharide (LPS)-stimulated inflammation and oxidative stress both in vivo and in vitro. Mechanistically, we found that CWA significantly reduced the LPS-induced nuclear translocation of NF-κB, thus decreasing the production of the pro-inflammatory cytokines TNF-α and IL-6 in macrophages. On the other hand, CWA markedly promoted the nuclear translocation of Nrf2 via the AKT pathway and p38 signaling. This resulted in increased expression of the anti-oxidative genes NQO-1 and HO-1 and alleviated oxidative stress in LPS-stimulated macrophages. Interestingly, the effects of CWA were diminished when AMPK was knocked down. Consistently, we noticed that CWA failed to ameliorate the LPS-induced inflammatory response and oxidative stress in AMPK knockout mice. Furthermore, we discovered that LKB1 was essential for AMPK activation by CWA. These data demonstrated for the first time that CWA attenuated LPS-stimulated inflammation and redox imbalance through regulating LKB1-AMPK signaling. Such knowledge provides new insights into the mechanisms through which Cathelicidin peptides modulate immune responses.