Titanium diboride (TiB2) is one of the candidate materials for high temperature structural applications and also for control rod elements in high temperature nuclear reactors. In this paper the nano-sized titanium diboride powders were synthesized through a borothermic reduction by using TTIP and B4C as titanium and boron sources. Three different concentration of TTIP solutions were prepared: 0.033, 0.050 and 0.10 M. After heat treating of products between 900 to 1200°C, the scanning electron microscopy (SEM) images and X-ray diffraction patterns of powder indicated that by using the 0.10 M TTIP, the only product was TiB2; otherwise the product was TiB2-B4C composite.