The relation between the molecular attributes of crumb rubber–modified asphalt (CRMA) fractions and the enhancement in the CRMA in-service properties was investigated. This was achieved by investigating the relation between the enhancement of the CRMA physical properties expressed in terms of its stiffness (complex modulus [G*]) and elasticity (phase angle [δ]) and the change in its molecular structure. Gel permeation chromatography analysis on the liquid phase of CRMA fractions was employed to characterize the change in the CRMA fractions (saturates, asphaltenes, naphthene aromatics, and polar aromatics). Research results showed that, for most of the samples, there is a marked difference in the weight average molecular weight and polydispersity index in relation to enhancement of the physical properties. This indicates that the crumb rubber–modified components played a role in the change of the internal structure of the CRMA, leading to enhancement in its physical properties and thus its expected in-service performance.