Research into asphalt binders that are resistant to high temperatures is essential. Many studies have modified asphalt with nanomaterials to increase asphalt's resistance to rutting. The purpose of this study is to examine nano crumb-rubber additives as possible modifiers of asphalt binder. Different percentages of nano crumb rubber, namely 1.2%, 2.4%, and 3.6% were added to the pure asphalt binder Pen 60/70 and extracted from Lawele Granular Asphalt. The viscosity test was run at different temperatures to observe how the modified asphalt performed during compaction and mixing. The purpose of the rheology test is to determine the value of the rutting factor in modified asphalt nano crumb rubber and pure asphalt binder using the Dynamic Shear Rheometer. The results show that complex shear modulus and phase angle values decrease with each additional % of nano crumb-rubber in modified asphalt. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.