Babassu (Attalea speciosa) is a typical oilseed from the Brazilian northeast that may be an alternative feedstock for biodiesel production. Generally, biodiesel is very susceptible to oxidation compared to mineral diesel, which represents a relevant disadvantage for storage and transportation. The presence of unsaturated compounds in biodiesel favors the initiation and propagation of oxidation reactions. In this study, the biodiesel samples were stabilized with three antioxidants: N,N'-disec-butyl-p-phenylenediamine (PDA), IONOL (a synthetic phenolic antioxidant), and unsaturated cardanol (a natural phenolic antioxidant). Then, the products were evaluated under accelerated conditions. The oxidation tests used the Rancimat method and the differential scanning calorimetry (DSC) method. The physicochemical properties of babassu biodiesel and its blends with the three antioxidants were within the limits of ASTM D6751. The results of accelerated experiments using the Rancimat method showed a significant improvement in the oxidative stability of the babassu biodiesel doped with PDA (>180 h) and IONOL (>55 h) for samples doped with 100 mg/kg. Using DSC, the thermal analysis enhanced the onset temperature of doped samples to 211.7 and 201.14 degrees C for PDA and IONOL, respectively. Doped samples with 100 mg/kg of unsaturated cardanol did not improve the oxidative stability of the pure babassu biodiesel sample. These results indicate a higher antioxidant activity of PDA when compared to the two phenolic antioxidants.