AbstractWood-plastic composites (WPCs) represent a growing class of durable, low-maintenance construction materials whose use can decrease dependence on petroleum. High-density polyethylene (HDPE), chitosan (CS), wood flour (WF), boric acid (BA), and borax (BX), as well as maleic anhydride grafted polyethylene (MAPE) and polyethylene wax (PE wax), were used to develop a durable wood-plastic composite (WPC) using the extrusion method. The effects of boron compounds (3%, 6%, 9%, or 12% by weight BA/BX) on the mechanical and fire properties of the WPCs were investigated. Mechanical testing indicated that as the percentage weight of boron compounds increased, the flexural modulus, flexural strength, and tensile strength significantly decreased. Cone calorimeter tests were used to characterize the fire performance of the WPCs, and these results suggested that adding BA/BX compounds to WPCs modestly improved the fire performance. As the percentage weight of BA/BX increased from 3% to 9%, the time to ignition (TTI), heat release rate (HRR), total heat release rate (HRR-Total), smoke production rate (SPR), and specific extinction area (SEA) of the WPCs were all reduced.