This article reported the synthesis of phosphorylated compounds derived from cardanol, a phenolic by-product of the cashew (Anacardium occidentale L.) industry, and its application as antioxidants for biodiesel. These compounds were added in biodiesel samples in three different concentrations (500, 1000 and 2000 ppm) and their antioxidants activities were tested by thermogravimetric analysis (TG), analyzing the onset (T-e) and endset (T-o) temperatures values as reference parameters, as also by evaluating their integral procedure degradation temperatures (IPDTs). The results showed that the addition of new antioxidants increased the thermal stability of biodiesel, making this biofuel more resistant to thermo-oxidative process. (C) 2012 Elsevier Ltd. All rights reserved.