In the present study, the efficacy of waste peels of mango (Mangifera indica) as a basic catalyst in room temperature transesterification reaction is investigated for biodiesel production from soybean oil. Biowaste based catalyst, Mangifera indica peel ash, was prepared by conventional open air burning of the mango peel. The morphology and chemical components of the catalyst are investigated using several techniques such as X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET) and Hammett indicator method. The highest biodiesel yield of 98% was attained under the optimized reaction conditions; methanol to oil ration of 6:1, catalyst loading of 6 wt %, and time of 4 h under room temperature. Crucially, the catalyst retained its activity up to 4th cycle of reused. The excellent catalytic activity of the ash catalyst could be attributed to the presence of highly basic metal oxides such as K2O, MgO and CaO, its high surface area and porous nature. (C) 2020 Elsevier Ltd. All rights reserved.