Objective: To investigate whether the ethanol extract of Chondracanthus tenellus (Harvey) Hommersand, a type of red algae, could exhibit anti-inflammatory potential in lipopolysaccharide (LPS)-stimulated macrophages. Methods: The ethanol extract of Chondracanthus tenellus was applied to 100 ng/mL LPS-stimulated RAW 264.7 cells, and cell viability, phagocytic ability, levels of pro-inflammatory factors, and the production of reactive oxygen species were measured. To identify the underlying mechanism of the ethanol extract of Chondracanthus tenellus, the expression of inflammation-regulated genes was estimated. Results: The ethanol extract of Chondracanthus tenellus had no cytotoxic effect at concentrations below 300 μg/mL, and reduced the LPS-induced production of inflammatory mediators including nitric oxide (NO) and prostaglandin E2. Furthermore, the extract markedly suppressed the expression of inducible NO synthase and cyclooxygenase-2, as well as the production of reactive oxygen species. The LPS-induced up-regulation of pro-inflammatory cytokines was attenuated by treatment with the ethanol extract of Chondracanthus tenellus, reducing their extracellular secretion. The Chondracanthus tenellus extract also inhibited LPS-mediated activation of nuclear factor-kappa B (NF-κB). In addition, the phosphorylation of mitogen activated protein kinases (MAPKs) and phosphatidylinositol 3 kinase (PI3K)/Akt was markedly increased by LPS, which was significantly abolished by the Chondracanthus tenellus extract. Conclusions: Our findings indicate that the ethanol extract of Chondracanthus tenellus exhibited potential anti-inflammatory and antioxidant effects through downregulating the NF-κB, MAPKs, and PI3K/Akt signaling pathways in LPS stimulated RAW 264.7 macrophages.