The large amount of disposable bottles presently produced makes the search for alternative products that reuse these materials imperative. Wood-plastic composites are sustainable, organic materials, that show potential for the development of environmentally friendly products. This paper presents the optimization of tensile and flexural strength of a wood-plastic composite made from polyethylene-terephthalate, as thermoplastic resin, and sawdust as fiberfill. The goal of this study was to establish the operating conditions that provide the optimum properties of the wood-plastic composites, with minimal variance. The particle size of the fiber filler was taken as a noise factor. The response surface methodology, by contour lines, in a combined design of experiment was applied.