Aimed to increase the load-bearing capacity of wood-plastic composites (WPC), sisal and glass fiber fabrics were incorporated into wood-high density polyethylene (HDPE) composites by sandwiching them inside the composites during the compression molding of extruded WPC pellets. Experimental results showed that the inclusion of long fibers in less than 20 wt% in the form of fabrics, particularly glass fabrics (13-20 wt%), could effectively enhance the mechanical performance of the wood-HDPE composites with significantly increased strength and modulus as well as the improved creep resistance, compared with their unreinforced counterparts. The reinforced WPC preserved their wood-like appearances, but they have much higher strength and creep resistance. Particularly, the WPC samples reinforced by two layers of glass fabrics could have strengths that were comparable to that of solid wood in the parallel-to-grain direction but much better mechanical performance than that of wood in the perpendicular-to-grain direction. Surface treatments to the fiber fabrics using a silane coupling agent and the incorporation of maleic anhydride-grafted polyethylene into the WPC pellets during the compounding process could improve the interfacial compatibility between the reinforcing fabrics and the HDPE matrix and, thus, resulted in additional increases in the mechanical performance of the composites. On the basis of the experimental results and the simplicity of the processing methods adopted in this study, the approach, which sandwiched natural or inorganic fiber fabrics into WPC, provided a feasible method to effectively improve the load-bearing capability of WPC products, which may allow the reinforced WPC to be potentially used in certain structural applications to replace solid wood.