The effect of phthalic anhydride as a coupling agent on the tensile properties and thermal stability of recycled high density polyethylene/wood fiber (rHDPE/WF) composites were studied. Both composites rHDPE/WF and rHDPE/WF/PAH (modified with phthalic anhydride) were prepared using Brabender Plasticorder at a temperature of 160°C and rotor speed of 50 rpm. The result indicated that rHDPE/WF/PAH composites exhibit higher tensile strength and modulus of elasticity than rHDPE/WF composites. It was also found that the addition of phthalic anhydride offers better thermal stability in rHDPE/WF/PAH composites than that of rHDPE/WF composites.