Plastic-containing waste causes significant environmental pollution because it remains in nature for a long time without degrading. This waste includes polyolefin-based containers, polyethylene terephthalate (PET) water bottles, and cardboard-polyethylene-aluminium beverage boxes. In recent years, important steps have begun to be taken to eliminate the environmental effects of plastic-containing solid waste. These have the goal of reducing these wastes by using them to produce new composite products. In this study, composite sheets were produced by mixing polypropylene (PP) obtained from recycling waste plastic furniture as a polymer matrix and waste Tetra Pak® boxes (TPBs) as a filler in different mixing ratios. Then, the density, thickness swelling, water absorption, flexural strength, flexural modulus, deformation at bending, tensile strength, tensile modulus, elongation at break, and hardness values of the produced sheets were determined. According to the data obtained, it was determined that as the amount of filler in the composite increased, the density, thickness swelling, water absorption, flexural modulus, tensile modulus and hardness values increased, whereas the flexural strength, deformation at bending, tensile strength, and elongation at break values decreased. According to the results obtained from the study, it can be said that new composites can be successfully produced using a waste PP-based polymer matrix and waste TPBs as filler.