Oxidation Stability is one of the most important fuel quality criterions for biodiesel and primarily affects the stability of biodiesel. Therefore, in the present work, antioxidant activity of ginger extract was studied as a method to increase oxidation stability of Pongamia pinnata biodiesel. Ginger extract is a nature based renewable substance and has antioxidant property. The presence of phenolic compounds in ginger extract was identified by HPLC, FT-IR and 1H NMR technique. The ginger extract was further characterized by BET, powder XRD, SEM and TEM techniques. The antioxidant activity of different concentrations of ginger extract was tested against radical 2,2-diphyny1-1-picrylhydrazyl (DPPH). A total of five treatments of Pongamia biodiesel doped with ginger extract i.e. 0 ppm (BG(0)), 250 ppm (BG(1),), 500 ppm (BG(2)), 1000 ppm (BG(3)), and 2000 ppm (BG(4)) were prepared for evaluating the oxidation stability. The oxidation stability of all the samples was evaluated with the professional biodiesel Rancimat instrument manufactured by metrohm. The results demonstrated that a minimum doping of 250 ppm of ginger extract in pongamia biodiesel has met both American (ASTM D-6751) and European(ENE14214) standard specifications for biodiesel Oxidation stability and can be used as antioxidant for biodiesel. These studies prove to be beneficial in the exploration of natural antioxidant sources for preservation of biodiesel which keeps its renewable nature intact unlike synthetic antioxidants which compromise the renewable nature of biodiesel because most of the synthetic antioxidants are made from petroleum sources. (C) 2016 Elsevier Ltd. All rights reserved.