This study investigated the mode of action between wood and thermoplastic interphases. For this purpose, the effect of sanding and chemical treatments on the wood surface wettability has been simultaneously evaluated. Contact angle measurements were tested on wood veneers (spruce) using Van Oss-Chaudhury-Good (VOCG) method to determine the surface free energies (SFE). To better understand the mechanism of treatments on the physical interactions, veneers were either/both sanded or/and treated by maleic anhydride grafted with polyethylene (MAPE) so that the analysis of surface pre-coating and its influence on the polarity and the dispersive properties of the wood-polymer interface can be further studied. The results showed a significant increment of both surface roughness and interfacial area after sanding which improved pre-coating of plastic on the wood surface consequently. Analysis of wetting parameter showed compatibility between two types of surface modification, as the treatment of veneers by sanding and MAPE together resulted in higher contact angles and lower surface free energy (SFE) on the wood surfaces. MAPE could entirely cover the wood veneers and form a non-polar surface, which suggests the effectiveness of this chemical and its compatibility with the sanding operation on the wood surface.