AbstractOil palm ash (OPA), a bio-agricultural waste from oil palm mills, was subjected to high-energy ball milling for 30 h and was converted into a nano-structured material. The nano-structured OPA was characterized for its particle size and crystallinity index by using Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) analysis. The crystallite size obtained from TEM and XRD was found to be 50 nm and 54.32 nm respectively, and the crystallinity index of OPA was 66.54%. The shape and texture of raw and nano-structured OPA were studied using scanning electron microscopy. The raw OPA had an irregular shape with spongy and porous structure, while the nano-structured powder had a mostly irregular and crushed shape. The elemental studies of OPA used Energy Dispersive X-ray (EDX) analysis, XRD, and Fourier Transform Infrared Spectroscopy (FT-IR). The elemental compositions found in OPA were silica, potassium oxide, calcium oxide, magnesium oxide, aluminium oxide, and iron oxide.