Acute inflammation is often observed during acute lung injury (ALI) and acute respiratory distress syndrome. Glucosamine is known to act as an anti-inflammatory molecule. The effects of glucosamine on acute lung inflammation and its associated mechanisms remain unclear. The present study sought to address how glucosamine plays an anti-inflammatory role in acute lung inflammation in vivo and in vitro. Using the LPS intratracheal instillation-elicited rat lung inflammation model, we found that glucosamine attenuated pulmonary edema and polymorphonuclear leukocyte infiltration, as well as the production of TNF-α, IL-1β, cytokine-induced neutrophil chemoattractant (CINC)-1, macrophage inflammatory protein (MIP)-2, and nitric oxide (NO) in the bronchoalveolar lavage fluid (BALF) and in the cultured medium of BALF cells. The expression of TNF-α, IL-1β, IFN-γ, CINC-1, MIP-2, monocyte chemotactic protein-1, and inducible NO synthase (iNOS) in LPS-inflamed lung tissue was also suppressed by glucosamine. Using the rat alveolar epithelial cell line L2, we noted that the cytokine mixture (cytomix)-regulated production and mRNA expression of CINC-1 and MIP-2, NO production, the protein and mRNA expression of iNOS, iNOS mRNA stability, and iNOS promoter activity were all inhibited by glucosamine. Furthermore, glucosamine reduced LPS-mediated NF-κB signaling by decreasing IκB phosphorylation, p65 nuclear translocation, and NF-κB reporter activity. Overexpression of the p65 subunit restored the inhibitory action of glucosamine on cytomix-regulated NO production and iNOS expression. In conclusion, glucosamine appears to act as an anti-inflammatory molecule in LPS-induced lung inflammation, at least in part by targeting the NF-κB signaling pathway.