Mechanical properties of tungsten heavy alloys are dependent on many factors including the purity of the raw materials, their tungsten content, manufacturing parameters and the microstructure of the final compact. The main object of this research was to examine the effect of sintering conditions (temperature and time) on the microstructure of tungsten heavy alloys and how the resulting modification of the microstructure can be used to optimize their mechanical properties. Alloys composed of 88%, 93% and 95% wt. of tungsten with the balance of Ni: Fe in the ratio of 7:3 were consolidated into green compacts. Samples of each of the three resulting alloys were sintered at different temperatures (1350°C,1450°C and 1500 0C) for different sintering holding times (3 and 30 minutes) in hydrogen atmosphere. Standard metallographic procedures were used to obtain SEM micrographs. The mechanical properties of tungsten heavy alloys were found to be dependent on the microstructural parameters such as W particle size, solid volume fraction, connectivity and w-w contiguity. It was shown that the mechanical properties of the alloys, and especially their ductility, are harmed when tungsten grains are contiguous.