This paper describes the antioxidant and anti-tyrosinase activity and chemical composition of the mesocarp of Attalea speciosa Mart. ex Spreng fruits (babassu, family Arecaceae). The total phenolic content determined with the Folin-Ciocalteu reagent was higher in the ethyl acetate fraction, hydroalcoholic fraction and hydroalcoholic extract. Antioxidant activity was assayed by the in vitro DPPH, ABTS, and FRAP assays. The highest antioxidant activity was observed for the ethyl acetate fraction which also has showed the highest levels of proanthocyanidins in the vanillin-HCl assay, which may be related to its greater inhibitory activity of mushroom tyrosinase. Analysis by HPLC-MS/MS has revealed the presence of nine compounds identified as (epi)catechin monomers and their oligomers. The presence of these compounds, which were identified for the first time in babassu mesocarp, is possibly related to the antioxidant and anti-tyrosinase activity of this palm tree.