The thermo-mechanical properties of asphalt mixtures are highly influenced by the properties of the asphalt binders. The poor performance of the asphalt binders can lead to several distresses in asphalt pavements such as rutting and fatigue cracking. One of the common approaches to mitigate the asphalt pavement distresses is modifying the asphalt binders, which can happen by using a wide variety of modifiers or additives. In this research, the effects of various amounts of a green composite modifier (CM) made from recycled materials on the performance of a base asphalt were investigated. In addition, using the same base binder, the performance of this modifier was compared with that of Styrene-ButadieneStyrene (SBS) which is the most common modifier used in many regions. The use of CM obtained from recycled materials can provide both environmental and economic benefits. It could also be expected to obtain technical improvements upon the addition of this modifier. The CM contained High-Density Polyethylene (HDPE), Ethylene Propylene Diene Monomers (EPDM), Ground Tire Rubber (GTR), and bitumen. The performance of the binders was evaluated by conducting a wide range of tests including penetration, softening point, viscosity, conventional performance grading, linear amplitude sweep, and multiple stress creep recovery. The findings from this research indicated that both modifiers improved the rheological properties of the binders. Moreover, although CM slightly showed negative impacts on the fatigue life, it was found to show comparable performance with that of SBS. (C) 2019 Elsevier Ltd. All rights reserved.