Polycrystalline diamond (PCD), due to its properties of mechanical resistance, high hardness and wear resistance, has special applications in cutting and drilling tools industries. As a result, more studies are needed looking for different ways to improve its performance and extend its useful life. Thus, this work introduced niobium, as a new binder for High Pressure-High Temperature sintering of polycrystalline diamond powders, in different concentrations (2.5, 5.0 and 10 wt%). The effect of High Energy Milling on the sintering process was also be investigated. All samples were sintered at a pressure of 7.7 GPa at 1750 °C. The obtained powder mixtures after milling showed a higher reduction in the average particle size as the Nb concentration increased, resulting in 46.21% reduction for 10 wt% Nb. Scanning Electron Microscopy (SEM) investigation of sintered bodies showed uniform dispersion of Nb between the diamond particles, in addition to the absence of crack formation during sintering. The X-ray diffraction (XRD) analyzes proved the thermal stability of the samples during the process, without graphitization.