In the present work, ultra-fine powder of oxide dispersion strengthened Alloy 617 was synthesized by high energy ball milling. Milling parameters such as rpm and milling time were varied in the range of 500-2000 and 5-360 min, respectively. Energy applied to the powder in the milling process (Energy per unit mass per hit, E-c) was estimated using the collision model. Effect of milling parameters on the microstructure of powder and refinement of oxides was investigated using X-ray Diffraction (XRD), Scanning electron Microscopy (SEM), conventional Transmission Electron Microscopy (TEM) and High resolution Transmission Electron Microscopy (HRTEM). Desired convoluted lamellar structure with average particle size similar to 33 mu m was observed during milling at 1000 rpm (E-c similar to 0.4 kJ/g.hit) for 6 h. TEM analysis of the powder showed the presence of fine oxide dispersoids in the size range 4-16 nm. HRTEM analysis substantiated the presence of fine dispersoids of size similar to 4 nm and showed the presence of deformation twins in the matrix. The fine dispersoids in a nanocrystalline matrix is expected to provide superior creep strength to the material at high temperatures. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.