Chemical structure and concentrations of coupling agents are the most important in choosing appropriate coupling action between polymer matrix and wood filler in composites. In this study, the efficiency of new amido-acrylic acid (AMACA) coupling agent synthesized for this propose at the Forestry Faculty of the Belgrade University, was compared with two well-known commercial coupling agents, anhydride of maleic acid (in the form of maleated polypropylene MAPP) and silane A-1100 (gamma-aminopropyltriethoxy silane). The polypropylene-wood flour (PP-WFl) composites were produced with 40% of wood particles having a fraction size of 0.3 mm. The melt-blended composites were modified with coupling agents in amounts of 1.7, 4.0 and 6 wt.% (based on wood filler) and successively with 0.05 wt.% (based on PP) of organic peroxide during the mixing step. The composites containing coupling agents showed superior mechanical properties, compared with the untreated ones. The highest extent of improvement of tensile and impact properties was achieved with PP-WFl composites modified by an AMACA coupling agent.