Plastic pollution has become one of the most pressing global environmental challenges. This issue was intensified in recent decades by the unprecedented increase in plastic consumption. Current waste management practices remain far from addressing the growing plastic footprint. Incorporating plastic waste into asphalt pavement presents a promising solution to consume significant quantities of plastic waste while improving pavement performance. This study investigates the use of High-Density Polyethylene (HDPE) plastic waste as a modifier in bitumen binders. Bitumen samples were prepared with shredded HDPE added at 1%, 2%, 3%, 4%, 5% and 6% by weight and underwent a series of laboratory tests to evaluate key bitumen properties. The HDPE-modified bitumen samples showed acceptable performance in terms of the softening point, penetration, mass loss, flash point and viscosity. In addition, the modified samples exhibited enhanced aging resistance compared with the unmodified bitumen. Optimal performance was observed at intermediate HDPE contents, achieving a balance between strength improvement and workability. The results demonstrate the potential of HDPE-modified asphalt as a durable and environmentally sustainable material for asphalt pavement applications.