Lasia spinosa (L.) Thwaites was used as a traditional medicine to treat many inflammatory diseases for centuries. However, its effects on the inflammatory response are not yet characterized. In this study, we investigated the anti-inflammatory activities of L. spinosa leaf extract in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. We found that ethanol extracts of L. spinosa leaves showed anti-oxidant activity due to the presence of high levels of polyphenolic compounds. Treatment with the leaf extract significantly repressed the production of inflammatory mediators such as nitric oxide and reactive oxygen species and the expression of pro-inflammatory cytokines in the LPS-stimulated RAW264.7 cells. Moreover, L. spinosa leaf extract treatment prevented activation of the nuclear factor-kappa B pathway by inhibiting nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) degradation. Furthermore, the mitogen-activated kinase and phosphoinositide-3-kinase/protein kinase B (PI3K/Akt) pathways were suppressed upon treatment with the leaf extract. In addition to suppressing inflammatory factors, the extract also activated the nuclear factor erythroid 2-related factor 2/heme-oxygenase-1 pathway. We propose that L. spinosa leaf extract has the potential as an effective therapeutic agent for alleviating oxidative stress and excessive inflammation.