Discrete element method (DEM) was employed to characterize the mixing of the solid particles in two different types of the powder blenders. In the first part of this study, DEM was used to investigate the effects of initial loading, drum speed, fill level, and agitator speed on the mixing efficiency of a slant cone mixer. DEM simulation results were in good agreement with the experimentally determined data, both qualitatively and quantitatively. In the second part of this study, DEM was employed to characterize the mixing of the solid particles in a Ploughshare mixer. To validate the model, the simulation results were compared to the positron emission particle tracking (PEPT) data reported in the literature. The validated DEM was then utilized to calculate the mixing index as a function of the initial loading, plough rotational speed, fill level, and particle size for a ploughshare mixer.