In this study, the B4C-TiB2-TiC composite powder was synthesized by mechanical alloying (MA) of Ti-B4C powder mixture. For this purpose, four powder mixtures of Ti and B4C powders with different molar ratios were milled. In order to study the mechanism of Ti-B4C reaction during milling, structural changes and thermal analysis of powder particles were studied by X-ray diffractometry (XRD) and differential thermal analysis (DTA). Morphology and microstructure of powder particles during milling were studied by scanning electron microscopy (SEM). It was found that during MA, after decomposition of the outer layers of B4C particles, first, C reacted with Ti and after that, B was diffused in Ti structure and TiC and TiB2 phases were formed in gradual reaction mode. Also, the results of DTA and thermodynamic analysis confirmed the suggested mechanism for Ti-B4C reaction. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.