Baccharis trimera is a widespread South American plant known as "carqueja". Medicinal teas prepared from the aerial parts of this plant are used in folk medicine in cases of liver diseases and inflammatory processes. We evaluated the effects of aqueous extract of B. trimera in the experimental inflammatory model of carrageenan-induced pleurisy in rat. The injection of carrageenan into the pleural cavity induces an influx of cells and fluid accumulation with a large number of polymorphonuclear leukocytes and increase of protein levels. The inflammation parameters were attenuated when B. trimera (400 and 800 mg/kg, i.p.) was administrated 30 min before the carrageenan. The immunomodulatory effects were evaluated in vitro on human peripheral blood mononuclear cells. The extract in concentration of 25, 50 and 100 mg/mL presented inhibited the T-lymphocytes proliferation stimulated by phytohemagglutinin, but these extract concentrations also presented cytotoxic effect. These results showed that the aqueous extract of B. trimera has anti-inflammatory effect.