The aim of this study was to investigate the chemical composition and the antiinflammatory/antinociceptive properties of the hydroalcoholic extract derived from the leaves of Phyllanthus brasiliensis (HEPB) in rodents. A new arylnaphthalene lignan glycoside, 5-O-β-d-glucopyranosyljusticidin B, together with six known lignans, were isolated from HEPB. 1D and 2D NMR experiments and HRMS were used to elucidate the structure of the new compound. HEPB toxicity and antinociceptive activity were evaluated through acute oral toxicity and formalin models in mice, respectively. The anti-inflammatory effects of HEPB were assessed using carrageenan- and dextran-induced paw edema models in rats. HEPB showed low toxicity. Oral administration of HEPB reduced paw edema induced by carrageenan, but not by dextran. HEPB and its fractions from FR6 to FR10 (FR6-10) inhibited the neurogenic and inflammatory phases of formalin-induced linking, demonstrating its antinociceptive activity. These results indicated that lignans from Phyllanthus brasiliensis exerted antinociceptive/anti-inflammatory effects not related to the histaminergic pathway.