The temperature and stress caused by the load can be cited as two main parameters leading to breakage in asphalt pavement, especially rutting (permanent deformation). So, to reduce the problems of rutting of roads, several actions have been taken, including improving pavement quality and the structure design methods. The increase in the attention of respective engineers in the last few years to modify and improve the asphalt performance through providing different types of additives and replacing the raw materials of asphalt mixture with recycled materials to improve the environment and reduce the cost of modified pavement mixture. This study discussed the use of low-density waste polyethylene as an asphalt modifier in percentages of (2, 4, and 6) % by the weight of asphalt and their impact on the performance of asphalt mixtures at high temperatures. This study showed that using plastic waste (low-density polyethylene) as a bitumen modifier improved the performance of asphalt mixtures at different high temperatures. This was achieved by reducing the rut depth by (80.5) % and (82.3) % at temperatures of 50 C and 60 C, respectively, using low-density polyethylene waste at an optimum value of about 4% by weight of asphalt in addition to enhancing the Marshall stability by using this percentage of polymer.