This study evaluated the chemical composition of freeze-dried jaboticaba peel (FJP) and jaboticaba peel aqueous extract (JE) and their antioxidant capacity in vitro and in vivo in obesity model. Phenolic compounds, total anthocyanins, flavonoids and antioxidant capacity (DPPH, FRAP, ABTS and ORAC assays) in FJP methanolic extract and JE were measured. Specific phenolics (ellagic and gallic acids) and anthocyanin (cyanidin-3-O-glucoside) were measured by LC-DAD-ESI/MS. In the biological assay thirty-six Wistar rats were divided in six groups: AIN-93 M normal control diet; HFF (obese control) feed a high-fat and fructose diet; Prevention FJP (P. FJP) and Treatment FJP (T. FJP) feed HFF diet with 2% of FJP powder, for 12 and 6 weeks respectively; Prevention JE (P. JE) and Treatment JE (T. JE) were feed with HFF diet and the water was substituted by JE, for 12 and 6 weeks, respectively. FRAP, TBARS, GSH and antioxidant enzymes (GPx, GR, CAT and SOD) were determined in the plasma and liver. The limit of significance was set at P b 0.05. The FJP methanolic extract showed higher levels of total phenolics and anthocyanins, ellagic acid and DPPH, FRAP and ORAC assay, but JE showed higher levels of cyanidin-3-O-glucoside, gallic acid and ABTS assay. Antioxidant potential of the FJP and JE were confirmed by important markers in animals, such as TBARS and GSH levels and CAT activity, but not by FRAP assay, and SOD, GR and GPx enzymes. Thus, FJP and JE showed an important antioxidant effect in vitro and in vivo.