Abstract Osthole has been reported to possess a variety of pharmacological activities, such as antiinflammatory effect. In the present study, we have investigated the effect of osthole on lung inflammation associated with carrageenan-induced pleurisy in rats. The result showed that osthole could inhibit significantly pleural exudates formation and PMNs infiltration. Histological examination revealed osthole could reduce lung inflammation in rats treated with carrageenan. The myeloperoxidase (MPO) level was examined in pleural exudates. The result showed that osthole could attenuate MPO level in pleural exudates. Further studies showed osthole could decrease tumor necrosis factor alpha (TNF-α) and interleukin 1beta (IL-1β) levels in the lungs. Taken together, the present results suggested that osthole could inhibit lung inflammation on carrageenan-induced pleurisy in rats and that could be related to a reduction of PMNs infiltration and release of inflammatory factors.