The effects of sintering conditions on the microstructural evolution and mechanical properties of mechanically alloyed tungsten heavy alloys were investigated. W, Ni and Fe powders were mechanically alloyed in a tumbler ball mill at a milling speed of 75 rpm, ball-to-powder ratio of 20:1 and ball filling ratio of 15%. The mechanically alloyed powders were compacted and solid-state sintered at a temperature of 1300 degreesC for 1 hour in a hydrogen atmosphere. The solid-state sintered tungsten heavy alloy was subsequently liquid-phase sintered at 1470 degreesC with varying sintering times from 4 min to 90 min. The solid-state sintered tungsten heavy alloy showed fine tungsten particles of 3 mum in diameter and high relative density above 99%. The volume fraction of the W-Ni-Fe matrix phase was measured, as 11% and tungsten/tungsten contiguity was 0.74 in solid-state sintered tungsten heavy alloys. Mechanically alloyed and two-step sintered tungsten heavy alloys showed tungsten particles of 6-15 mum and a volume fraction of the W-Ni-Fe matrix phase of 16% and tungsten/ tungsten contiguity of 0.40. The solid-state sintered tungsten heavy alloy exhibited a yield strength of about 1100 MPa due to its finer tungsten particles, while it showed low elongation and impact energy due to its large tungsten/tungsten contiguity. The yield strength of two-step sintered tungsten heavy alloys increased with the decreasing of tungsten particle size and volume fraction of the W-Ni-Fe matrix.