Due to the rapid urbanization of a country like India, the increasing generation of waste plastic has become a severe environmental issue because of its imperishable nature. Incorporating waste plastic in a bituminous mixture as road construction is a sustainable solution to the abovementioned issue. Apart from the disposal issue, with the increase in the traffic load intensity, the road performs poorly mainly in water- induced conditions so, polymer-like polyethylene terephthalate (PET), polypropylene (PP), high-density polyethylene (HDPE) and low-density polyethylene (LDPE) are used as additives or modifiers. The current study investigates the effect of using PET in the bituminous mixture as a binder modifier. In this regard, samples were prepared with different binder percentages (4 to 6% at 0.5% increments) as a conventional mix, and the modified mixes were prepared with varying PET content (2 to 8%). The optimum bitumen content (OBC) was further calculated using the Marshall Mix design method corresponding to 4% air void as per MS 2 guidelines. The experimental outcomes show that the inclusion of PET improves the consistency characteristics and penetration index of the modified bitumen compared to the conventional one. Also from the performance test, it was observed that the mixes prepared with modified bitumen revealed improvement in results in terms of Marshall Stability, moisture susceptibility characteristics, and rutting characteristics. The optimum PET content (OPETC) was determined using obtained experimental values.