In this study, low density polyethylene (LDPE) and triethanolamine (TEOA) were used together by applying a different process in order to obtain a good chemical interaction between LDPE and bitumen in bitumen modification and the effects of this interaction on the performance properties of bitumen were investigated. For this purpose, modified bitumens were obtained by adding 2.5 wt% TEOA and different proportions (1, 2, 3, 4, and 5 wt%) of waste LDPE to pure B 70/100 bitumen. Physical and rheological properties of pure and modified bitumens were determined by conventional and Superpave tests, and microstructural characterizations were determined by SEM, XRD, and FT-IR spectroscopy tests. As a result of the tests, it was observed that phase separation disappeared by forming a good chemical interaction between bitumen and LDPE. In addition, it has been determined that with the addition of LDPE, the binders come to a hard consistency and their temperature sensitivity decreases, but they retain their elasticity properties. It was determined that especially 4% LDPE added binders showed a significant increase in permanent deformation, fatigue and thermal crack resistance, which are performance properties at high, intermediate, and low temperatures, respectively.