CONTEXT Polygala sabulosa, popularly known as "timutu-pinheirinho," has been used in Brazilian folk medicine for the treatment of bowel and kidney disorders and as an expectorant. OBJECTIVE Evaluate the anti-inflammatory effects of the crude extract (CE), acetonic fraction (Ac), and the main compound, 7-prenyloxi-6-methoxycoumarin (PC) on a mouse model of carrageenan-induced pleurisy. MATERIALS AND METHODS A mouse model of carrageenan-induced pleurisy was used to investigate the effects of P. sabulosa CE, Ac and PC on leukocyte migration, exudate formation, activities of myeloperoxidase (MPO), and adenosine-deaminase (ADA), levels of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β) and nitric oxide (NO). In addition, the effect of the plant material on lung histology was also evaluated. The effects of PC on the TNF-α, IL-1β and NO synthase 2 (NOS2) mRNA expression, were also investigated. Finally, the effect of PC on the nuclear factor-kappa B (NF-κB) and p38 mitogen-activated protein kinase (p38 MAPK) was also evaluated. RESULTS CE, Ac and PC reduced inflammation in the pleural cavity and lungs. This effect was evidenced by reduction on all inflammatory parameters evaluated; the exception being the inability of the CE to inhibit exudate formation. In isolation, PC showed reduction on mRNA levels of TNF-α, IL-1β and NOS2, and on activation of the NF-κB and p38 MAPK pathways. CONCLUSION The presented results show that P. sabulosa has significant anti-inflammatory activity, as does its main compound, PC. Moreover, the results suggest that PC exerts its effects mainly by inhibited the NF-κB and p38 MAPK pathways.