A rapid and easy synthesis of pure neodymium hexaboride, NdB6 nanocrystals was developed, without applying heat treatments at high temperatures. The mechanochemical synthesis of NdB6 powders was performed at room temperature inside a planetary ball mill. The Nd, B2O3 and Mg starting blends were mixed, and subsequently mechanically alloyed to constitute NdB6-MgO as final products. The effect of milling duration on the NdB6 formation mechanism and metallothermic reduction was investigated. Following mechanochemical synthesis, MgO was removed from the system by leaching the powders with CH3COOH solution. The formation of NdB6 phase was monitored by the X-ray diffraction (XRD) analysis. Microstructure and morphology of the synthesized nanocrystals were characterised by using scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS), and high resolution transmission electron microscopy (HRTEM) techniques. Pure NdB6 nanocrystals with a crystallite size of 18.2 +/- 2.0 nm were obtained after 15 h of milling. Microscopic investigations revealed the irregular shape and morphology of NdB6 nanocrystal structures. Rietveld refinements confirm the cubic structure (space group Pm-3m) with a lattice constant of 4.1254 (2) angstrom and 92 +/- 8 nm particle size of NdB6 phase. The Raman active phonons of Pm-3m symmetry were characterised by Raman spectroscopy.