This study aimed to investigate the combination effect of glycerin treatment and thermal modification of wood flour on the physical, mechanical, thermal dynamic mechanical properties of wood flour/polypropylene (PP) composite. The morphological aspect was also investigated. The wood flour was first impregnated in the aqueous solution of glycerin, followed by heat treatment at 200°C for 1 h. Then the unmodified or modified wood flour was blended with PP at a weight ratio of 4:6 to prepare composites. Moisture adsorption experiment and X‐ray photoelectron spectroscopy analysis of wood flour demonstrated that the hygroscopicity and the free surface hydroxyl groups of wood flour decreased after glycerin‐thermal modification. Thickness swelling of the 10% wt glycerin‐thermally modified wood flour/PP composite was reduced by 42.8% after 96 h immersion as compared to unmodified control. Evaluation of mechanical properties in impact and flexure modes indicated that glycerin treatment alone had no significant effect, but the combination of glycerin and thermal treatment slightly decreased the strength, with the exception of 10% glycerin and heat modified sample. Dynamic mechanical analysis and scanning electron microscope illustrated the improved interfacial bonding between PP and wood flour modified by 10% glycerin and heat treatment. POLYM. COMPOS., 35:201–207, 2014. © 2013 Society of Plastics Engineers