To investigate the properties of wood flour/high-density polyethylene composites (WF/HDPE) filled with different kinds of mineral components (CaCO3, talc powder, and wollastonite), WF/HDPE was prepared via a molding method. The thermal properties of WF/HDPE were analyzed with a comprehensive thermal analyzer, and the mechanical properties were measured. The moisture resistance was indicated by 24 h water absorption. The results indicated that both the mechanical and physical properties of WF/HDPE samples were improved remarkably by adding CaCO3, talc powder, or wollastonite. The tensile strength with talc powder was 83% higher than the composites without the additive. The maximum residual weight of the composites with added talc powder was 21.8% at 600 °C, which was 7.47% higher than that of the composites without additive. The composites with added talc powder exhibited better water resistance. Additionally, scanning electron microscopy (SEM) showed that the addition of talc powder enhanced the interaction between the components.