The rise in plastic waste is attributed to the varied types and sizes of containers used for liquids like mineral water, oils, detergents, etc. This increase in solid waste, which is driven by population growth, developmental activities, and changes in lifestyle, has led to a significant global issue. Plastic waste, known for its durability and lack of aesthetic appeal, poses a challenge in its disposal. This study aims to explore the Marshall engineering properties of asphalt mixtures infused with recycled plastic from water bottles (polyethylene terephthalate or PET) at concentrations of 0.25%, 0.5%, 0.75%, and 1% relative to the weight of the aggregates. The findings indicate that the inclusion of plastic improves the asphalt's stability to a certain point, beyond which its effectiveness diminishes due to the excessive plastic content. The study establishes that incorporating 0.5% plastic into the asphalt mixture meets all the criteria of the Marshall test, including stability, flow, air voids, VMA, and VFA. Therefore, it is concluded that 0.5% is the optimal percentage for the addition of plastic to enhance the Marshall properties of an asphalt mixture.