In this paper, the particle shape and size of tungsten powders were quantitatively analyzed by image analysis technology, and the effect of particle shape on the rheological properties of tungsten feedstocks for metal powder injection molding (MIM) was alao investigated. The results showed that the particle size of narrow particle-sized tungsten (NPW) powder was almost the same as that of spherical tungsten (SW) powder. In contrast to NPW powders, the SW powders exhibited better sphericity, surface smoothness and dispersion. Mixing with the same binder, the solid loading of SW powders was 64%, which was higher than that of 59% of the NPW powders. The SW feedshocks showed better flow performance, i.e., lower flow behavior index and flow activation energy, and it thus was more suitable for injection molding. Particle shape affects the rheology of tungsten MIM feedstocks by changing the nature of organic binder–particle and particle–particle interactions.