Abstract: The sintering microstructure and densification behavior of the spherical and irregular tungsten powders prepared by hot pressing (HP) and hot isostatic pressing (HIP) were systematically investigated. In the results, the irregular FW9 powders achieve the densification through coupled grain boundary diffusion and plastic flow during HIP stage, whereas the spherical SW15 and SW25 powders exhibit the progressively reduced densification efficiency dominated by plastic flow and surface diffusion mechanism, respectively. Notably, the broad particle size distribution of SW25 powders critically constrains the densification process. The FW9 sintered compacts display the average dislocation density of 0.577×10¹⁴ m⁻², the low-angle grain boundaries (LAGBs) of 24.4%, the wide grain size distribution of 25～250 μm, and the average grain size of 76.04 μm with the pronounced crystallographic texture. In contrast, the SW15 and SW25 sintered compacts show the higher average dislocation densities of 0.800×10¹⁴ m⁻² and 1.300×10¹⁴ m^–2, the elevated LAGB fractions of 62.4% and 75.0%, and the uniform grain sizes of 44.68 μm and 50.15 μm, respectively, without the preferential orientation, indicating the intensified lattice distortion and plastic deformation in spherical powders during sintering. It is demonstrated that the spherical powders significantly enhance the grain size uniformity, suppress the abnormal grain growth, and avoid the texture formation, providing the critical insights for tailoring high-performance tungsten sputtering targets through powder morphology optimization.