Asphalt modifiers/additives are increasingly used in pavement industry. Additives are commonly used as softeners to decrease the binder performance grade (PG), while polymer modifiers are usually used for heavy traffic applications to reduce permanent deformations. Recently, rejuvenators have been used in recycled pavement applications to reduce cracking susceptibility and as retarders to moisture damage. These modifiers can be derived from crude petroleum and sometimes from a bio-based feedstock. The origin of crude binder and modifier source affects the resulting binder-modifier chemical interaction. The inherent chemical variability affects the rheological performance of modified binders. It also impacts the aging potential of these binders and thereby affecting its long-term field performance. In this study, binders modified with softeners/rejuvenators at various dosages were evaluated for their performance under long-term aging. Rheological characterization of modified binders was determined using frequency sweep, linear amplitude sweep, and low temperature performance with parameters such as Glover-Rowe, R-value, crossover frequency, ΔTc, while the chemical characteristics were determined using Fourier transform infrared spectroscopy (FTIR), and thin layer chromatography and flame ionization detection (TLC-FID). An optimum dosage of the rejuvenator studied was recommended to maximize performance of the modified binder.