The rapid mechanochemical synthesis of nanocrystalline CuFeS2 particles prepared by high-energy milling for 60 min in a planetary mill from copper, iron and sulphur elements is reported. The CuFeS2 nanoparticles crystallize in tetragonal structure with mean crystallite size of about 38 +/- 1 nm determined by XRD analysis. HRTEM study also revealed the presence of nanocrystals with the size of 5-30 nm with the tendency to form agglomerates. The Raman spectrum confirms the chalcopyrite structure. Low temperature magnetic data for CuFeS2 support the coexistence of antiferromagnetic and paramagnetic spin structure. Moreover, the hysteresis loops taken at temperatures from 5 K to 300 K revealed a presence of very small amount of ferromagnetic phase, which seems to be associated with the non-consumed elemental Fe in as-prepared nanoparticles. The optical band gap of CuFeS2 nanoparticles has been detected to be 1.05 eV, larger than band gap of the bulk material. The wider gap possibly resulted from the nanosize effect. Photoresponses of CuFeS2 nanoparticles were confirmed by I-V measurements under dark and light illumination. It was demonstrated that mechanochemical synthesis can be successfully employed in the one step preparation of nanocrystalline CuFeS2 with good structural, magnetic, optical and electrooptical properties. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.